Yes, you will most likely see the opposite sector on an SA and interferer list. This is normal. Even with some distance between AP’s, the amount of energy coming out the back of the radio and/or reflecting off near by surfaces will show up on an SA or scan. ePMP (and other AP’s like PMP450), don’t know how to distinguish between one another from an energy perspective (they can see each other from a frame perspective). The keys in GPS sync are to make sure that the clients don’t hear the AP facing the opposite direction, and that the AP’s are using a common time source so that they transmit at the same time.
Just follow Cambium’s GPS sync guide to make sure your using the appropriate settings. Check the logs for loss of sync.
If using back to back frequency reuse, and any of your sync’d radios goes into internal sync mode, this will cause major issues… like poor modulation, and de-registered clients.