@droftarts and @Phaedrux
Yes it was exaclty this, Thankyou. I'm not sure how i got there, but i spent the best part of two full weekends battling over this. You've saved me from insanity.

Oooh, thansk all, that makes sense.

looks like i've miss assigned my end stops as low end, shoudl be M574 X2 A1 P"xstop" etc.

I'll give this a try and report back.

Hi All,

I've been having difficulties with setting up my machine and i'm now getting some really weird behavior out of it.

I recently updated from firmware 2.03 to 3.1.1, and did a fresh setup of the machine. I'm using the standard setup from the reprap configurator.

Hardware is a duet 2 wifi, Anycubic predator (delta), BL touch.

I have found that sometimes on power-on it will refuse to home and says "position not reachable from current location" (or similar). I find this happens when it power-on resets with a Z position that is technically higher than the Z travel. In addition, i've found that it will refuse to G92 the Z height close to the maximum Z. For example, on my Z stop, i want to set a G92 height of 451mm, but it instead sets is some random figure about 10mm below this. I've also found it does this with the homing script, so the maximum height gets reset to some random number, close to but not quite the actual Z height limit.

I found by modifying the Z height to be larger than it actually is in the startup M556 command would make this o away, but that caused other issues. Instead, i've been trying to home against the switches, then drop 50mm and G92 the position, but that now gives the below really weird behavior. Homing script:

; homedelta.g
; called to home all towers on a delta printer
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Mon Jul 20 2020 14:35:08 GMT+1000 (Australian Eastern Standard Time)
G91 ; relative positioning
G1 H1 X705 Y705 Z705 F1800 ; move all towers to the high end stopping at the endstops (first pass)
G1 H2 X-5 Y-5 Z-5 F1800 ; go down a few mm
G1 H1 X10 Y10 Z10 F360 ; move all towers up once more (second pass)
G4 P200
G92 Z400
G1 H0 Z-50 F1800 ; move down a few mm so that the nozzle can be centred
G4 P200
G90
G92 Z400
G1 H0 Z5 X0 Y0
G4 P200
G30
G1 H0 Z100 X0 Y0
G4 P200

I recently updated from 2.03 to 3.1.1 because I found when i homed the machine and then did a G1 X0 Y0 Z0, or similar move, the effector would sometimes move about 30mm above the bed, but in a random X and Y position. This was especially weird because sometimes it would work perfectly after a power reset, but most of the time it behaved badly.

Earlier today, i powered it on and got a G28 "failed to enable endstop" error, which was new for me and especially worrying because it wasn't doing it last night, and i haven't changed anything.

I was worried i'd screwed up the firmware update anyway from previous, so i took it out of the machine earlier today and followed the fallback update procedure #1 from the firmware update page, and i was initially pleased i might have fixed it, but i'm still getting the G28 end stop error and now can't make the machine move at all.

Not sure how to upload config.g directly, so print out below. All i've changed from the configurator setup (apart from homing script) is to comment out the M501 command because i thought i might have some weird auto calibration settings that were causing the random moves.

Thanks in advance for any help.

; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Mon Jul 20 2020 14:35:06 GMT+1000 (Australian Eastern Standard Time)

; General preferences
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves
M550 P"Goyds_delta" ; set printer name
M665 R227 L440 B160 H451 ; Set delta radius, diagonal rod length, printable radius and homed height
M666 X0 Y0 Z0 ; put your endstop adjustments here, or let auto calibration find them

; Network
M552 S1 ; enable network
M586 P0 S1 ; enable HTTP
M586 P1 S0 ; disable FTP
M586 P2 S0 ; disable Telnet

; Drives
M569 P0 S0 ; physical drive 0 goes backwards
M569 P1 S0 ; physical drive 1 goes backwards
M569 P2 S0 ; physical drive 2 goes backwards
M569 P3 S1 ; physical drive 3 goes forwards
M584 X0 Y1 Z2 E3 ; set drive mapping
M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z80.00 E837.00 ; set steps per mm
M566 X1200.00 Y1200.00 Z1200.00 E1200.00 ; set maximum instantaneous speed changes (mm/min)
M203 X18000.00 Y18000.00 Z18000.00 E1200.00 ; set maximum speeds (mm/min)
M201 X3000.00 Y3000.00 Z3000.00 E1000.00 ; set accelerations (mm/s^2)
M906 X1000 Y1000 Z1000 E800 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Axis Limits
M208 Z0 S1 ; set minimum Z

; Endstops
M574 X1 S2 P"xstop" ; configure active-high endstop for high end on X via pin xstop
M574 Y1 S2 P"ystop" ; configure active-high endstop for high end on Y via pin ystop
M574 Z1 S2 P"zstop" ; configure active-high endstop for high end on Z via pin zstop

; Z-Probe
M950 S0 C"exp.heater3" ; create servo pin 8 for BLTouch
M558 P9 C"^zprobe.in" H5 F100 T1000 ; set Z probe type to bltouch and the dive height + speeds
G31 P25 X0 Y-40 Z2.4 ; set Z probe trigger value, offset and trigger height
M557 R120 S20 ; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0 ; map heated bed to heater 0
M143 H0 S80 ; set temperature limit for heater 0 to 80C
M308 S1 P"e0temp" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit

; Fans
M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T60 ; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

; Miscellaneous
;M501 ; load saved parameters from non-volatile memory