Not sure if anyone else has this problem, but I have a Nuki Bridge and since upgrading to the Unifi U6 Lite AP the bridge constantly goes offline after about 5 minutes. Does not happen with the NanoHD
Maybe the communication is restricted for the Bridge?
Make sure that it can use the outgoing port 443, so it can build up a connection to the Nuki server.
I have two bridges the one inside connects to the nanoHD perfectly and has never disconnected. The one on the U6 is online for maybe 10 minutes then disconnects and never reconnects. It’s sitting right next to the AP
Try to make a port forwarding or a dmz temporarily for the bridge, to look if it works then, if yes, at least you know then, that the firewall is the issue, and can try to twist on the firewalls settings, to get it working!