How interesting, another community user had the same battery issue on WatchOS 10.5, Apple Watch Battery Drain after updating … - Apple Community, heres what they said to fix this issue:
Try force resetting your Apple Watch. Press and hold both the side button and Digital Crown until the screen turns black and the Apple logo reappears, then release both buttons. Your watch might take a few moments to restart.
After try unpair and repair your Apple Watch with your iPhone. Go to the Watch app on your iPhone, go to watch list, select the info on your Watch, select Unpair Apple Watch, then repair.
If the issue still persists, contact Official Apple Support.
For more information: If your Apple Watch is stuck on the Apple logo - Apple Support