audBall sums it up well above.
I was referring to keeping everything in place and the same, except swapping the microphone amplifier-bodies back and forth from the left to right channel and vice-versa. If the inverted polarity moves with the microphone body, that's were the issue is.
Leaving the amplifier bodies in place and swapping just the capsules back and forth would let you know if it's one of the capsules rather than one of the amplifier-bodies, but I suspect it's one of the amplifier bodies, with the simple mis-wiring problem audBall notes above.
Once you determine that, record a single hand-clap using both microphones. Zoom in with your editor to see which microphone shows the first cycle at the very beginning of the clap waveform going down instead of going up. That's the one with the inverted polarity problem. Mark that mic so you'll know which channel to invert when editing, or send that mic to your tech and ask him to check the wiring to pins 2 and 3 of the microphone's XLR connector. He probably just needs to switch the wiring to those two pins.