If i remember correctly my default Homeall.g came with positive homing moves that i had to change to negative, could it be that you have the axis inverted and also have the homing backwards?

Does unplugging the motor (power off board first) connector from the board clear the error? And make sure you don't have a bit of metal shorting out the underside of the board. If you cant clear the error by removing the connector a good visual inspection might be a good idea.

In my experience a stepper motor that stalls easily and suddenly moves in a random direction is a good indication that one of the stepper coils is not connected or has a bad connection. How much of the wiring and connector are you not changing? If you plug everything including all wiring/connectors/motor that you plug in to E1 to the E0 port will it still have issues?

@pugzor Yay, glad it was a easy fix.

Cool! Looking forward to more details and specs:)

Are you using a 3 or 4 point leveling system? I ask because my custom printer has a similar 2020 (?) bed frame I experimented with a single beam in the center (T shape) to support the front center of the bed and also the way you have it with two beams on each side. (U shape)
It looked like to me that having a single beam in the center would allow less flex for the bed. (in the roll direction if you will) My thinking was if one side flexed up 1 mm and the other 1mm down it would be a 2mm difference, but with the T shape the flex in theory would only be that 1mm (for a example) but i guess you would have more weight on one beam. Perhaps I'm just overthinking it:)

@pugzor Yup! So the issue is not be the board, that's good news. I'm not sure if the Duet will show this type of error if you have the motor wired wrong ie if you have a coil connected across the two coil outputs but i would guess not, mostly likely your extuder motor cable actually does have the wires shorted out together or to a grounded metal frame.

Just to be clear, you still get the short to ground error message on driver 3 when you try and command a move of driver 3 without anything connected to that board connector correct? I'm trying to determine if the board has a fault or the issue is the extruder motor/wiring (driver3?) that is at fault.

Does unplugging the motor (power off board first) connector from the board clear the error? And make sure you don't have a bit of metal shorting out the underside of the board. If you cant clear the error by removing the connector a good visual inspection might be a good idea.

I was having vary similar issues as this with a E3D sensor, it was not always a spike but a 20-30c error at times then other times it would spike to the max. Replacing it solved all issues even though it was a new barely used sensor.

Have you measured the actual current of the bed at full power? My KEENOVO 500w 120v AC heater pad draws around 4.8A at 120v AC so 580W or so. It may be that your closer then you think to the max of your 600W PSU or even over it you include hotend and motors.

You should be able to connect both negatives of the power supply's together directly on the negative of the board.
Then one or both of the positives on the heaters to the matching power supply, as with most controllers the Duet will switch the ground connection so it will still control correctly.

If i remember correctly my default Homeall.g came with positive homing moves that i had to change to negative, could it be that you have the axis inverted and also have the homing backwards?