Drove to the base of the mountain where I was able to connect a SM to the bad AP. No problem getting access to it from the wireless side. The bad AP reported a 1 Gbps connection on the Ethernet port but it was unable to connect out or ping anything. Matches the behavior from the other side of that port.
I downgraded from 3.5 to 3.2.2. AP came back up after a reboot and was working as normal.
I then upgraded from 3.2.2 to 3.4.1. No problems after reboot. All working normal.
I then upgraded from 3.4.1 to 3.5. After the reboot, the AP would not connect to anything on its Ethernet port. It was essentially dead to the world again.
Downgraded back to 3.4.1 and everthing is fine again.
So, as far as I can tell, there is an issue with the 2000 hardware and 3.5. I have 2 other 2000 APs but I am not really willing to test this theory on them since it's pretty disruptive to my customers.
The system log was downloaded during the 3.5 upgrade when it would not connect via Ethernet but there is nothing of interest in there other than cnmaestro trying to connect.
** UPDATE** For kicks, I uploaded 3.5RC7 to the AP. Same behavior as 3.5 - no communication out the Ehternet port.
For now, running 3.4.1 with no issues. I am happy to send the json config file to Cambium for lab testing to reproduce this.