As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE T/S FOR RT GEN INOP, APU GOT TRIPPED OFF WITH CROSS-TIE LOCKOUT, FOUND BROKEN TERMINAL ON RELAY R2-40. TERMINAL HAD ARCED AND WORN ON A WIRE BUNDLE CAUSING DAMAGED WIRING. ARCING WAS FOUND WHILE AC ON GROUND DURING MTC. REPLACED RELAY AND REPAIRED DAMAGED WIRING.