show started and everything seemed fine
about 1 minute in there is a noise like someone hit the mic cap with something (which I know didn't happen)
about 6 minutes in the file gets "hotter" and the overall volume goes up
Is this on both channels or just 1? If it is both, then I wouldn't focus on the individual XLR connections. It it's one channel, I would focus on the XLR's.
Does you TB have a "high power/low power switch"? My LB does, and one time I accidentally ran my Gefells (which need 48v) with the switch set to lower power. It passed sound but without adequate voltage the mics brickwalled.
Regarding the event of "about 1 minute in there is a noise like someone hit the mic cap with something".... I've seen cases where capsules are bothered by moisture, and it usually makes a distinctive "sizzle.... pop!". If you pull it up in an editor the wave will creep towards top or bottom extreme, then quickly jump to the other extreme, then decay back towards the center. If this happens, that channel will probably be noisy all night. Normally this would only effect 1 channel, but I've seen cases where it will also effect the other channel a little as well.
Any flakeyness with the battery/cable powering the TB? I had that once. Normally I think of a flakey battery cable as being off or on, one or the other, no in between. But in the case of my LB things faded away and come back... I didn't suspect the battery cable at first... I was looking for other connections. The way you said "overall volume increased after a few minutes" makes me wonder if your battery situation improved at that point as you were maybe wiggling things around. This would effect both channels.
Edit: Just realized I answered a 3 week old post. I presume you found something? What was it?