@r8a1l4, would like to confirm the scenario you have mentioned, to gain a better understanding of the situation.
[AP One Ent] <-----PoE Input-----> [802.3af PoE (Injector / Switch)] <----> [UPS] <-----> [AC Input Power]
AP One Ent operating condition:
1. AC Input Power interruption occurs
- UPS kicks in with backup power to power the AP One Ent
- AP One Ent still power on and working normally to provide Wi-Fi connectivity
2. AC Input Power restored
- UPS return to normal condition
- AP One Ent is rebooting at this moment
Can you share the details of the PoE Switch and the PoE Injector, as well as the type of UTP cable used in the environment?