[diverson]

Just an update, I still haven't found any piece of metal or debris that could be causing the short. Whatever did it must be gone already, just leaving the damage behind. A continuity test confirms that the 5V bus is shorted to ground at the DIOs, the analog input, and the SPI connector.

As Chris predicted, switching the jumper did not clear the fault. The conformal coating makes probing difficult, but I was able to determine that the USB-A connectors are the only place where I can still see 5V. I'm guessing it must be running from its own VReg, and maybe even opto-isolated.

The only real source of heat seems to be U13, but I can't tell what kind of IC it is. Again, the conformal coating makes this difficult.

I'm out of ideas at the moment, so please let me know if anybody else has an idea of where to go from here.

Dean