Thanks for the help Ian, here's what I've got:
M115 response:
FIRMWARE_NAME: RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 3.0 ELECTRONICS: Duet WiFi 1.02 or later FIRMWARE_DATE: 2020-01-03b3
I swapped the motors and cables with the two others and all motors have the same effect.
I also tried your config and just had one Z axis motor on E1 using the config here:
; Drives
M569 P0 S1 ; physical drive 0 goes forwards
M569 P1 S1 ; physical drive 1 goes forwards
M569 P2 S1 ; physical drive 2 goes forwards
M569 P3 S1 ; physical drive 3 goes forwards
M584 X0 Y1 Z4 E3 ; set drive mapping
M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z2560.00 E420.00 ; set steps per mm
M566 X900.00 Y900.00 Z12.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z180.00 E1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2)
M906 X800 Y800 Z800 E800 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout
But unfortuantely the same problem. Actually I tried running a motor from every driver by running through these M584 lines one at a time:
M584 X4 Y1 Z0 E3 ; set drive mapping
M584 X0 Y4 Z1 E3 ; set drive mapping
M584 X0 Y1 Z3 E4 ; set drive mapping
And none of them worked correctly. E0, E1, and X drivers made the motor 'twitch' and using the Y driver made the motor hum like crazy until I resetted. Again, I tried this with multiple other working motors and cables and the motors have nothing on the drive shaft.
So basically only the Z driver is spinning motors correctly. Any ideas? I feel like I'm stuck at step 0 here...