I wanted to piggyback onto this as i have the same issue. (DuetWIFI coreXY build with IR probe, X and Y endstops are on high ends of build plate i.e 300, 290)
I was running 1.19 and was having connectivity issues to the webcontrol UI, but no issues with homing.
I updated just the other day to 1.20, and when i ran homeall, x and y homed, then z crashed to the bed.
So i recalibrated my z probe per the wordpress article, and the z probe was triggering as expected at the same value i had set before in G31. I tested G30 S-1, AND G30 both probed the bed and stopped before a crash.
My thought is that in the release notes there was mention of adding S2 to the M574 section, but doing that just caused the x and y to crash, never getting to Z.
Below is my config.g and homeall.g files, maybe someone can shed some light on this for me.
–---Config.g:-------
; Configuration file for testing Duet Ethernet and Wifi
; Communication and general
M111 S0 ; Debug off
M550 PHC300 ; Machine name and Netbios name (can be anything you like)
M551 Pcheats5 ; Machine password (used for FTP)
;*** If you have more than one Duet on your network, they must all have different MAC addresses, so change the last digits
M540 P0xBE:0xEF:0xDE:0xAD:0xFE:0xED ; MAC Address
;*** Networking - Enable for both WiFi and Ethernet boards.
M552 S1 ; Turn network on
;*** Ethernet networking: Adjust the IP address and gateway in the following 2 lines to suit your network
M552 P10.10.10.250 ; (0 = DHCP)
M554 P10.10.10.1 ; Gateway
M553 P255.255.255.0 ; Netmask
M555 P2 ; Set output to look like Marlin
G21 ; Work in millimetres
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves
; Disable Fan 1 thermostatic mode
M106 P1 H-1
; Axis and motor configuration
M569 P0 S0 ; Drive 0 goes forwards
M569 P1 S0 ; Drive 1 goes forwards
M569 P2 S1 ; Drive 2 goes forwards
M569 P3 S1 ; Drive 3 goes forwards
M569 P4 S1 ; Drive 4 goes forwards
M574 X2 Y2 Z0 S0 ; set endstop configuration (all endstops at high end, active high)
;*** The homed height is deliberately set too high in the following - you will adjust it during calibration
M667 S1 ; switch to CoreXY mode
M208 X0 Y0 Z0 S1 ; Set axis minima
M208 X290 Y240 Z270 S0 ; Set axis maxima
M666 X0 Y0 Z0 ; put your endstop adjustments here, or let auto calibration find them
M350 X16 Y16 Z16 E16:16 I1 ; Set 16x microstepping with interpolation
M92 X80 Y80 Z400 ; Set axis steps/mm
M906 X500 Y500 Z500 E1120 I40 ; Set motor currents (mA) and increase idle current to 40%
M201 X1500 Y1500 Z1000 E1000 ; Accelerations (mm/s^2)
M203 X1000 Y1000 Z200 E3600 ; Maximum speeds (mm/min)
M566 X1200 Y1200 Z1200 E1200 ; Maximum instant speed changes mm/minute
; Thermistors
M305 P0 T100000 B3950 R4700 H30 L0 ; Put your own H and/or L values here to set the bed thermistor ADC correction
M305 P1 T100000 B3974 R4700 H30 L0 ; Put your own H and/or L values here to set first nozzle thermistor ADC correction
M305 P2 T100000 B3974 R4700 H30 L0 ; Put your own H and/or L values here to set 2nd nozzle thermistor ADC correction
M570 S180 ; Hot end may be a little slow to heat up so allow it 180 seconds
; Adjustments for J-heads used as dummy heaters on test rig
M307 H0 A250 C140 D5.5 B1
M307 H1 A250 C140 D5.5 B0
M307 H2 A250 C140 D5.5 B0
M557 X0:250 Y0:225 S25 ;mesh grid probe pattern
; Fans
M106 P1 S-1 ; disable thermostatic mode for fan 1
; Tool definitions
M563 P0 D0 H1 ; Define tool 0
G10 P0 S0 R0 ; Set tool 0 operating and standby temperatures
;*** If you have a single-nozzle build, comment the next 2 lines
;M563 P1 D1 H2 ; Define tool 1
;G10 P1 S0 R0 ; Set tool 1 operating and standby temperatures
M92 E837:837 ; Set extruder steps per mm
M143 H1 S290 ;set max hot end temp
M307 H1 A576.4 C196.8 D6 B0 S1 ;Set PID values for hot end
M143 H0 S125 ;set max bed temp
M307 H0 A146.6 C693.4 D9 B0 S1 ;Set PID values for Bed Heater
; Z probe and compensation definition
;*** If you have a switch instead of an IR probe, change P1 to P4 in the following M558 command
M558 P1 X0 Y0 Z1 ; Z probe is an IR probe and is used for homing Z axis
G31 Z1.5 P500 ; Set the zprobe height and threshold (put your own values here)
;*** If you are using axis compensation, put the figures in the following command
M556 S78 X0 Y0 Z0 ; Axis compensation here
;M208 S1 Z-1.95 ; set minimum Z
T0 ; select first hot end
-------Homeall.g–-------
G91 ; relative mode
G1 S1 X340 Y340 F3000 ; course home X or Y
G1 S1 X340 ; course home X
G1 S1 Y340 ; course home Y
G1 X-4 Y-4 F600 ; move away from the endstops
G1 S1 X10 ; fine home X
G1 S1 Y10 ; fine home Y
; Z homing section follows for IR Z probe
G1 X-30 F3000 ; X offset to get z probe to bed
G1 S1 Z-400 F500 ; course home Z
G1 Z2 F500 ; move away from the Z Probe
G1 S1 Z-4 F100 ; fine home Z
G90 ;back to absolute mode
G92 Z1.5 ;tell printer that it is at Z=1.5 (trigger height of z probe during homing)
One connector set was different than the other two which caused the issue.