I was struggling with same issue as described above for a long time until I came across this chain. Setting PDM_FOR_EXTRUDER 0 did the trick. For about about two days...
It now reappeared and can't seem to get rid of it.
ATX power supply just switches off. Nothing in the log, firmware appears to be running fine: I only have to do M81 and M80 (doing just M80 does not work - I guess the firmware thinks it is still in the on-state). Then it just turns off again (can be after seconds, but also after 2 minutes).
It only happens when also the heated bed is turned on. I also noted something else: when the heated bed is turned on, the temperature of the extruder is much less stable - it moves around quite a bit. Without heated bed turned on, the temperature stays on target almost perfectly.
Heated bed and extruder are fed by separate circuits from ATX power supply, which should have more than enough power. I've also recently moved from Marlin which I have been using without problems (well... without this one I mean).
Any further suggestions (not already made above)?