ePMP 1000 GPS AP lite - 3rd CPE won't register without reboot

Edison has been upgrading and we're experiencing 14~18 hour periods with no line power over the last 2 weeks.  UPS units are exhausted so the AP goes offline.  In this sample we have 2 APs with 3 CPEs each.  When the power comes back, 2 CPEs register but we have to go and physically power cycle the third.  Every time. This is on both APs, separated by serveral miles and is 100% repeatable.  Six times in the last two weeks, exact same behavior on both APs and the same CPEs each time.  Firmware has been updated to 3.5.2.  No change.  All radios are ePMP 1000 GPS lite.

Any ideas?