It was disconnected pin, I got hung up with short to ground error and was focusing on trying to find a short. Looks like on the side closest to the fuses one or more pins weren't connected, I did skimp a bit on the heat on that edge due to proximity of other components so ran a dry soldering iron over each pin and back to life now with all drivers working again. Many thanks.

@dc42 Failed again on beta4 (M122 at bottom) they are posted already but will group together here.

config.g

[PLA] CFFFP_Top - ReRender - zero temps (1).gcode

full sys directory: https://www.viaraix.net/duet3-sys.zip

=== Diagnostics ===
RepRapFirmware for Duet 3 MB6HC version 3.2-beta4 running on Duet 3 MB6HC v0.6 or 1.0 (standalone mode)
Board ID: 08DJM-956L2-G43S4-6J9FA-3S86T-1B5LD
Used output buffers: 1 of 40 (11 max)
=== RTOS ===
Static ram: 123212
Dynamic ram: 168584 of which 704 recycled
Never used RAM 99692, free system stack 188 words
Tasks: NETWORK(ready,169) ETHERNET(blocked,110) HEAT(blocked,298) CanReceiv(blocked,947) CanSender(blocked,371) CanClock(blocked,358) TMC(blocked,54) MAIN(running,1113) IDLE(ready,19)
Owned mutexes:
=== Platform ===
Last reset 00:00:19 ago, cause: software
Last software reset at 2020-11-27 11:41, reason: MemoryProtectionFault mmarValid daccViol, GCodes spinning, available RAM 99692, slot 2
Software reset code 0x4163 HFSR 0x00000000 CFSR 0x00000082 ICSR 0x0044a804 BFAR 0x00000000 SP 0x204100c8 Task MAIN
Stack: 00000002 ffffffff 00434a29 20410308 000002bc 00469483 0046a3c8 610f0000 2042565c 004691bf 2042565c 00000000 000002bb 0000000a 2042565c 204256c8 00000000 00000001 00000000 00468e53 204256c8 00000000 204256c8 004691bf 00000000 00000000 20425540
Error status: 0x00
MCU temperature: min 39.0, current 39.4, max 39.9
Supply voltage: min 23.9, current 24.0, max 24.0, under voltage events: 0, over voltage events: 0, power good: yes
12V rail voltage: min 12.0, current 12.1, max 12.1, under voltage events: 0
Driver 0: position 0, standstill, reads 32774, writes 14 timeouts 0, SG min/max 0/0
Driver 1: position 0, standstill, reads 32775, writes 14 timeouts 0, SG min/max 0/0
Driver 2: position 0, standstill, reads 32776, writes 14 timeouts 0, SG min/max 0/0
Driver 3: position 0, standstill, reads 32777, writes 14 timeouts 0, SG min/max 0/0
Driver 4: position 0, standstill, reads 32779, writes 14 timeouts 0, SG min/max 0/0
Driver 5: position 0, standstill, reads 32782, writes 11 timeouts 0, SG min/max 0/0
Date/time: 2020-11-27 11:41:21
Slowest loop: 6.06ms; fastest: 0.15ms
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 25.0MBytes/sec
SD card longest read time 0.7ms, write time 0.0ms, max retries 0
=== Move ===
Hiccups: 0(0), FreeDm: 375, MinFreeDm: 375, MaxWait: 0ms
Bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 0, completed moves 0, StepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed moves 0, StepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters = 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
SBC is idle in state(s) 0
Daemon is idle in state(s) 0
Aux2 is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 17.56ms; fastest: 0.03ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions Telnet(0), 0 sessions
HTTP sessions: 1 of 8
- Ethernet -
State: active
Error counts: 0 0 0 0 0
Socket states: 5 2 2 2 2 0 0 0
=== CAN ===
Messages queued 79, send timeouts 177, received 0, lost 0, longest wait 0ms for reply type 0, free buffers 47

It was disconnected pin, I got hung up with short to ground error and was focusing on trying to find a short. Looks like on the side closest to the fuses one or more pins weren't connected, I did skimp a bit on the heat on that edge due to proximity of other components so ran a dry soldering iron over each pin and back to life now with all drivers working again. Many thanks.

I previously destroyed Z stepper driver on my Duet2 due to own stupidity (mixed phases, let the smoke out and reports over temperature / short to ground).

This board has since been replaced so thought I would try repairing myself. So I cracked out the reflow station and after a short while old driver was removed and new driver installed. Visually apart from a bit of a scorch to plastic for plugs everything looks good.

However I still get over temperature / short to ground error coming up from driver 2 but now on top of this none of the other drivers work all reporting phase A/B may be disconnected.

Is it totally dead? As mentioned visually I cannot see any issues even under magnifying glass all pins look lined up perfectly and no shorts to neighbouring pin (except intended pairs).

As mentioned not crucial as I have replaced but would be nice to have a spare for another project.

@dc42 received replacement board from E3D today and working as expected in standalone, will get round to putting SBC back in this week but happy there shouldn't be any further issues.

Thank's again to yourself and @chrishamm for the help

@dc42 MCU was over reading by ~2C so adjusted to compensate and showing ~35C now.

Installed new firmware and...

30/11/2020, 13:26:02	Finished printing file 0:/gcodes/[PLA] CFFFP_Top - ReRender - zero temps.gcode, print time was 1h 41m

So looked promising so without changing anything I reran print to make sure it was not a fluke and sure enough it was ...

=== Diagnostics ===
RepRapFirmware for Duet 3 MB6HC version 3.2-beta4+4 running on Duet 3 MB6HC v0.6 or 1.0 (standalone mode)
Board ID: 08DJM-956L2-G43S4-6J9FA-3S86T-1B5LD
Used output buffers: 1 of 40 (12 max)
=== RTOS ===
Static ram: 123212
Dynamic ram: 168584 of which 704 recycled
Never used RAM 99692, free system stack 122 words
Tasks: NETWORK(ready,165) ETHERNET(blocked,105) HEAT(blocked,297) CanReceiv(blocked,947) CanSender(blocked,352) CanClock(blocked,349) TMC(blocked,20) MAIN(running,1113) IDLE(ready,19)
Owned mutexes:
=== Platform ===
Last reset 00:12:51 ago, cause: software
Last software reset at 2020-11-30 14:18, reason: MemoryProtectionFault mmarValid daccViol, Move spinning, available RAM 99692, slot 1
Software reset code 0x4164 HFSR 0x00000000 CFSR 0x00000082 ICSR 0x00427004 BFAR 0xb6d799a8 SP 0x2045ff58 Task MAIN
Stack: 00000060 000000c0 00000091 96969694 00000001 00468c29 00469614 8100000e 00455a21 0045f237 00000000 2040e064 a5000001 008e0d8e 2040e064 a5000001 00000000 00000001 204281fc 00469d17 0000a5c7 204103b4 2042820c 204281f0 204281fc 20428370 00000000
Error status: 0x00
MCU temperature: min 34.2, current 34.3, max 36.3
Supply voltage: min 23.9, current 24.0, max 24.0, under voltage events: 0, over voltage events: 0, power good: yes
12V rail voltage: min 12.0, current 12.0, max 12.1, under voltage events: 0
Driver 0: position -3200, standstill, reads 61020, writes 17 timeouts 0, SG min/max 0/156
Driver 1: position -800, standstill, reads 61021, writes 17 timeouts 0, SG min/max 0/319
Driver 2: position 2000, standstill, reads 61022, writes 17 timeouts 0, SG min/max 0/184
Driver 3: position 0, standstill, reads 61024, writes 17 timeouts 0, SG min/max 0/182
Driver 4: position 0, standstill, reads 61027, writes 14 timeouts 0, SG min/max 0/0
Driver 5: position 0, standstill, reads 61031, writes 11 timeouts 0, SG min/max 0/0
Date/time: 2020-11-30 14:31:40
Slowest loop: 12.11ms; fastest: 0.21ms
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 25.0MBytes/sec
SD card longest read time 0.9ms, write time 0.0ms, max retries 0
=== Move ===
FreeDm 375 (min 372), maxWait 727688ms, bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 13, completed moves 13, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 1], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed moves 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters = 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
SBC is idle in state(s) 0
Daemon is idle in state(s) 0
Aux2 is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 12.92ms; fastest: 0.03ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions Telnet(0), 0 sessions
HTTP sessions: 1 of 8
- Ethernet -
State: active
Error counts: 0 0 0 0 0
Socket states: 5 2 2 2 2 0 0 0
=== CAN ===
Messages queued 3089, send timeouts 6944, received 0, lost 0, longest wait 0ms for reply type 0, free buffers 47

@dc42 Thank you, will get in touch with E3D. Many thanks for your help.

@dc42 thanks for your time looking into this. Purchase was from E3D but I have just gone over the 6 months now (purchased 13th May), will you be able to authorise warranty replacement as reported prior?

@dc42 Failed again on beta4 (M122 at bottom) they are posted already but will group together here.

config.g

[PLA] CFFFP_Top - ReRender - zero temps (1).gcode

full sys directory: https://www.viaraix.net/duet3-sys.zip

=== Diagnostics ===
RepRapFirmware for Duet 3 MB6HC version 3.2-beta4 running on Duet 3 MB6HC v0.6 or 1.0 (standalone mode)
Board ID: 08DJM-956L2-G43S4-6J9FA-3S86T-1B5LD
Used output buffers: 1 of 40 (11 max)
=== RTOS ===
Static ram: 123212
Dynamic ram: 168584 of which 704 recycled
Never used RAM 99692, free system stack 188 words
Tasks: NETWORK(ready,169) ETHERNET(blocked,110) HEAT(blocked,298) CanReceiv(blocked,947) CanSender(blocked,371) CanClock(blocked,358) TMC(blocked,54) MAIN(running,1113) IDLE(ready,19)
Owned mutexes:
=== Platform ===
Last reset 00:00:19 ago, cause: software
Last software reset at 2020-11-27 11:41, reason: MemoryProtectionFault mmarValid daccViol, GCodes spinning, available RAM 99692, slot 2
Software reset code 0x4163 HFSR 0x00000000 CFSR 0x00000082 ICSR 0x0044a804 BFAR 0x00000000 SP 0x204100c8 Task MAIN
Stack: 00000002 ffffffff 00434a29 20410308 000002bc 00469483 0046a3c8 610f0000 2042565c 004691bf 2042565c 00000000 000002bb 0000000a 2042565c 204256c8 00000000 00000001 00000000 00468e53 204256c8 00000000 204256c8 004691bf 00000000 00000000 20425540
Error status: 0x00
MCU temperature: min 39.0, current 39.4, max 39.9
Supply voltage: min 23.9, current 24.0, max 24.0, under voltage events: 0, over voltage events: 0, power good: yes
12V rail voltage: min 12.0, current 12.1, max 12.1, under voltage events: 0
Driver 0: position 0, standstill, reads 32774, writes 14 timeouts 0, SG min/max 0/0
Driver 1: position 0, standstill, reads 32775, writes 14 timeouts 0, SG min/max 0/0
Driver 2: position 0, standstill, reads 32776, writes 14 timeouts 0, SG min/max 0/0
Driver 3: position 0, standstill, reads 32777, writes 14 timeouts 0, SG min/max 0/0
Driver 4: position 0, standstill, reads 32779, writes 14 timeouts 0, SG min/max 0/0
Driver 5: position 0, standstill, reads 32782, writes 11 timeouts 0, SG min/max 0/0
Date/time: 2020-11-27 11:41:21
Slowest loop: 6.06ms; fastest: 0.15ms
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 25.0MBytes/sec
SD card longest read time 0.7ms, write time 0.0ms, max retries 0
=== Move ===
Hiccups: 0(0), FreeDm: 375, MinFreeDm: 375, MaxWait: 0ms
Bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 0, completed moves 0, StepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed moves 0, StepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters = 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
SBC is idle in state(s) 0
Daemon is idle in state(s) 0
Aux2 is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 17.56ms; fastest: 0.03ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions Telnet(0), 0 sessions
HTTP sessions: 1 of 8
- Ethernet -
State: active
Error counts: 0 0 0 0 0
Socket states: 5 2 2 2 2 0 0 0
=== CAN ===
Messages queued 79, send timeouts 177, received 0, lost 0, longest wait 0ms for reply type 0, free buffers 47

@dc42 any update on this?

@dc42 Thank you.

Config attached, not been changed from assertation failure (or from 3.1.1). No filament monitors.

config.g

Simulation loop ran for 4 1/2 hours (~380 loops) with no issues.

Ripped 24V PSU out of another printer today and unplugged heaters and fans so just steppers and sensors plugged in and done another test print, again this did not complete.

This time M122 back to Memory Protection Fault

=== Diagnostics ===
RepRapFirmware for Duet 3 MB6HC version 3.2-beta3.2 running on Duet 3 MB6HC v0.6 or 1.0 (standalone mode)
Board ID: 08DJM-956L2-G43S4-6J9FA-3S86T-1B5LD
Used output buffers: 2 of 40 (11 max)
=== RTOS ===
Static ram: 122236
Dynamic ram: 168580 of which 376 recycled
Never used RAM 101000, free system stack 200 words
Tasks: NETWORK(ready,161) ETHERNET(blocked,109) HEAT(blocked,297) CanReceiv(blocked,948) CanSender(blocked,371) CanClock(blocked,356) TMC(blocked,54) MAIN(running,1111) IDLE(ready,19)
Owned mutexes:
=== Platform ===
Last reset 00:00:20 ago, cause: software
Last software reset at 2020-11-21 19:46, reason: MemoryProtectionFault mmarValid daccViol, Platform spinning, available RAM 101000, slot 1
Software reset code 0x4160 HFSR 0x00000000 CFSR 0x00000082 ICSR 0x00427804 BFAR 0x00038100 SP 0x2040aa78 Task TMC
Stack: 00000001 2040a928 00000000 00410210 00000000 00469d0f 00415682 21000000 427a0001 3c800001 00000000 3d000001 00000000 00000000 37533333 43d697a0 00000000 41dde946 43fa0000 44a80000 2040ff38 00469d0f 00000000 40078000 20400020 00415681 0000001e
Error status: 0x00
MCU temperature: min 39.2, current 39.9, max 40.0
Supply voltage: min 23.9, current 24.0, max 24.0, under voltage events: 0, over voltage events: 0, power good: yes
12V rail voltage: min 12.0, current 12.1, max 12.1, under voltage events: 0
Driver 0: position 0, standstill, reads 35967, writes 14 timeouts 0, SG min/max 0/0
Driver 1: position 0, standstill, reads 35968, writes 14 timeouts 0, SG min/max 0/0
Driver 2: position 0, standstill, reads 35969, writes 14 timeouts 0, SG min/max 0/0
Driver 3: position 0, standstill, reads 35970, writes 14 timeouts 0, SG min/max 0/0
Driver 4: position 0, standstill, reads 35971, writes 14 timeouts 0, SG min/max 0/0
Driver 5: position 0, standstill, reads 35975, writes 11 timeouts 0, SG min/max 0/0
Date/time: 2020-11-21 19:46:54
Slowest loop: 6.26ms; fastest: 0.15ms
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 25.0MBytes/sec
SD card longest read time 0.8ms, write time 0.0ms, max retries 0
=== Move ===
Hiccups: 0(0), FreeDm: 375, MinFreeDm: 375, MaxWait: 0ms
Bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 0, completed moves 0, StepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed moves 0, StepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters = 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
SBC is idle in state(s) 0
Daemon is idle in state(s) 0
Aux2 is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 5.46ms; fastest: 0.03ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions Telnet(0), 0 sessions
HTTP sessions: 1 of 8
- Ethernet -
State: active
Error counts: 0 0 0 0 0
Socket states: 5 2 2 2 2 0 0 0
=== CAN ===
Messages sent 82, send timeouts 82, longest wait 0ms for type 0, free CAN buffers 46