Thunderbolt Bridge not longer working in macOS 11.3

I use a Thunderbolt Bridge setup to directly connect to my QNAP NAS (TVS-872XT). Obviously, I have a unique IP setup for that connection, which is not conflicting with my Ethernet network.

When I updated from 11.2 to 11.3, the Thunderbolt Bridge stopped working entirely. Leaving the Network settings, and leaving the Thunderbolt cable plugged into a Thunderbolt port on my iMac, the boot time increases to 4 minutes.

The second I reboot without the Thunderbolt cable to my NAS plugged in, all is fine.

My other Thunderbolt devices all work fine, and my 2nd iMac which is running an older OS, also connected to QNAP via TB3 to the QNAP, is working fine via Thunderbolt Bridge.

WTF is going on?!