Is a 2018 Marshall MG50FX Service Manual available?  I have a unit which I fixed by reflowing the headphone module solder connections to the main control board but when I add the PEDL-90008 foot controller the current draw from the foot switch stops the amp from working properly after a few minutes.  Letting the amp sit for a bit then a factory reset seems to bring it back.  I suspect the power supply overheats due to current draw.