If you have tried several times and it doesn't work, I guess it might be brick during the upgrading? You can ask TP-Link support for help.

Seems strange, how could it reset such punctually? What the distance between the AP and PoE adapter? It should be within 60 meters with a Ethernet cable with good quality.

Seems like there is something abnormal during the communication between the APs and controller. You can try to re-install the AP controller and re-adopt the EAPs, this might help.

In normal case, the management VLAN and static IP settings will not lost after power loss or manual reboot. i'm able to access the Webinterface Did you try to login the EAP's web interface or use EAP...

Is there any interference near the EAP220? You can do a spectrum analyse, I met the similar problem with SSID disappearing, and as a result it's caused by an interference. You can try to change...

Suggest you to upgrade EAP to the latest software version and reinstall the EAP controller to have a try.