@dc42 It always happens when trying to home the machine after a software reset. Right now I can easily reproduce it:
power on the whole machine
do a homing cycle - everything is OK during this run if none of the end-stops is triggered
do an emergency reset through the web interface
try to home again the machine - the errors start popping up
I can't blame it any of the connectors because the errors do not come up after the initial power on. Also, if instead of trying to do a complete homing sequence I try to home a specific axis, the errors will come up for that axis. Even more, as I have a dual-Y setup, when I try homing the Y axis, the errors come up for both drivers/steppers.
Once the machine is homed, I can used for days with no errors!
More to that: the machine is a QueenBee mechanics (similar to WorkBee), with high torque steppers left from the original WorkBee - 3A, 4mH, 1.2Ohm.