Latest update killed the watch - Help!

OK, about 10 days ago, there was an update to the Watch OS. (7.3.2.1, I think).

As soon as it was installed, the watch started acting up - mostly the battery going dead all of a sudden after a full charge and so on. It would also restart on its own...

I've unpaired it from the phone, completely reinstalled it (presumably with the full, buggy update) and it kept doing the same thing.

Yesterday I gave it another go, this time there was an update option available (7.3.3). Unpaired, re-installed and did the update.

Guess what? Still happening.

Any help would be appreciated!