If the sources are synced and aligned, you can zoom in to look at the large, low-bass waveforms which should be all going up or down pretty much across all channels more or less evenly. If one channel or a pair is obviously going down on the largest half-waves when the others are going up, invert polarity on that channel or pair. But regardless of the visual appearance, rely mostly on flipping polarity back and forth while listening for the difference in the bottom end.
Could be caused by different mic locations. Might be on set of the PFAs (my PFAs invert my DPAs). Could be an XLR cable with pin 2 & 3 crossed.