Hardware Need help with switch possible power problems

[LIY2012]

I have a 1st gen switch that I'm having problems with that I hope someone can give me some advice. The previous owner had done some work on the switch, but I don't know everything that they did. There is evidence that the pi3USB and BQ had been replaced.

The switch can enter RCM mode, boot Hekate, LockpickRCM, etc. Everything seems to work fine, I can dump the eMMC, keys look good, fuse count matches firmware. However, anytime I try to boot, the system powers off.

If I try to boot OFW, nothing shows on the screen, not even the Nintendo Logo.
If I try to dump keys in LockpickRCM, it powers down when it tries to load SEPT.
If I try to dump keys with biskeys, it dumps the keys to USB and the screen flashes the keys and then goes black.
If I try to dump pkg1/pkg2 from Hekate, the screen goes black and powers off.
If I try to boot CFW, it shows the splash screen and then goes black.

I've checked the 3.3 v and 1.8 v rails and they seem fine.

Does anyone have any ideas on what could be going on here? Is it a power system problem? Could it be the MAX77621 buck converter?

I'd like to be able to test before I just start replacing components.

Any advice would be appreciated.