theifish I have run into the same issue with my Garmin Venu 3S watch and the Phone 2. The issue was not present in the beta. Sometimes after re-pairing it disconnected within minutes!
I checked some BT settings in the developer settings and saw that Gabeldorsche was deactivated. I activated it and restarted both the phone and the watch and paired the watch again. This time it stayed connected for several hours instead of just minutes.
When it had disconnected again and I checked developer settings again, I saw that Gabeldorsche was deactivated again!
Hoping for a fix soon!