Thanks much for helping to investigate this, FurryNutz!
I recall seeing last week the Internet Globe LED lit up blue, and the 5GHz radio LED slow blinking on the 880L bridge.
Just before this long weekend, I set up my 880L bridge and 868L bridge running alongside each otherl, both connecting to the same Netgear router SSID over 5GHz WPA2/AES. The 868L has the usual 8 clients attached (via a Netgear GS116 gigabit switch) and the 880L has just one client attached directly.
I just checked connectivity. It's been 3 days since the setup. The clients behind the 868L bridge are all responding to remote access (via TeamViewer). The single client behind the 880L bridge does not respond to remote access, most likely because the 880L has cut off internet connection to this client.
For lack of any evidence to the contrary, I still suspect this issue is related to 880L breaking client IP address renewals. After rebooting the 880L, connected clients all get normal IP address leases, and remain connected to the internet within their lease periods. Once a lease expires for a client, however, its internet connection will fail. By comparison, the 868L bridge working in the same environment as the 880L does not exhibit this issue.
At least the failure symptoms have remained highly consistent for this 880L, for as long as I have worked with it as a wireless bridge.