If it is so hard to find a repro, it can't be all that common...

You say it happened only three times. In how many performances? And you can't make it happen at home?

I think one of the things I'd suggest you try is a small, inexpensive UPS. House power can vary radically, not just from venue to venue, but at different times. If, for instance, the house A/C and the house freezers/walk-in fridges all power up at the same time, the power browns out a bit, and that's not something you are likely to ever encounter again.

On the whole, a UPS is the first thing I'd try. If you can't get it to lock up at home with a whole bunch of button pushing, it may not be the issue. But a whole lot of different things, from computers, to DVR's, to modems etc. can be VERY intolerant of drops in voltage. $30-40 ought to be enough to get one, and even if it doesn't cure this particular problem, you can still use it at home for your rig there...