Possible wiring damage ??
Once had a case where power was split 4 ways backstage, from a 125K Genny.
Runs 1 and 2 were stage right/left
Run 3 was FOH
Run 4 was a stringer for concessions (Not my idea, I was there day 3 for 2nd opener - no say in anything)
Anyhoo, run #4 was fine on light loads. Someone plugged in a popcorn machine in the middle of the run, and we lost FOH power.
Well, down to 80 volts or so. Me and Lampey's UPS both start screaming for attention. Put my troubleshooter hat on, and as I am talking up and down the concession line, to see who has and doesn't, I see a tent spike pretty freakin close to the power trench. Sure nuf, they nicked the feeder. Under a light load there was no problem. No blown breakers, but all problems dissapeared after pulling the spike (with well insulated gloves and pliers)