Troubleshooting the Makerhawk Load Tester

[samthelion17]

I recently bought this device and it was supposedly "used_like_new" but it didn't work so I tried to return it. Long story short: they didn't want it back, gave me credit and I got to keep it, but now gotta fix it.

It turns on but when I rotate the knobs it doesn't draw power from the load input (short video). When I removed the fan to check the power mosfet (IRFP264) I noticed a scorch mark near the schottky diodes (STPS41H100CG) and one contact pin of the nearby USB port missing.

IDK what happened there... I turned on my meter, measured the diodes and the mosfet and I think they're all OK. I connected a laptop power supply and measured some voltages in that area and this is what I got:

Some time later I measured the big SMD diode (SS56) next to the input screw terminals and found it to be faulty (dead short) so I replaced it but it didn't change anything.
I'm waiting for this power mosfet to arrive 'cause i'm not 100% sure if the one that it's currently installed is faulty or not but IDK what else to do or what else to look for.

Thanks in advance!