A new transformer/meter/disconnect or just a new 3 phase disconnect?
We traced the install all the way to the pole. It all seemed to be brand new conduit. There had only been single phase service at this club before. That would seem to indicate a new transformer as well.
A bad/missing neutral connection can cause the same symptoms. The real danger being that they can cause an overvoltage on a piece of gear and ultimately damage something.
I watched the production company connect his tails. He gave each a good tug to make sure they were secure. We went back to each cam lok junction and made sure that each was securely tightened. I also kept an eye on the volt meters. They hovered between 115 and 121.
I moved the monitor rig to another circuit on a different leg leaving only the bass player's wireless, the tracks rack and the drum thumper on leg three thinking that we could continue the show without any of those things. After moving the monitor supply, the surge would alternate between the legs...