We have a 450i that it appears lost sync after firmware update to 20.3.1.1. Logs show that it acquired sync right after the update but lost it soon after. Sync is being provided by Packetflux PoE injector plus sync. There is another AP on the same injector that is getting sync without any issues.
I am not seeing any indications of a cable/connector issue. Consistent 1 Gbps with no Ethernet errors reported on AP or switch.
Soft reboot did not fix it. I guess a hard reboot would be my next step.