do all SMs in sector disconnect or only some? Did you check what is going on on SM side? Spectrum, log messages, SNR, RSSI? You can have interference on SM side and it can be intermittent.
Also you can submit a support ticket https://support.cambiumnetworks.com/, attach Tech Support Files from AP and couple SMs in question and we will try to sort your issue.
To grab TSF:
GUI >> Tools >> Backup / Restore >> Backup Technical Support File
This sounds like interference that is causing the AP to no hear the SMs. Take a long timed spectrum scan from the AP and when all of the SMs drop off you will have an indication of what is happening.
If you have an SM that you can drop to wifi mode and search the area with then I highly suggest doing so.
This is not exclactly what your having but it may provide a clue as to what to look for.
We commonly get complaints that there is a problem with our service only to find out the customer just got a new WIFI router and the 5ghz is left at auto and high power. Have them quickly set the 5ghz AP to specific frequency that we provide and have them drop the default power down and the problem goes away.