My issue was that Watchtower would sporadically just fumble the update, making re-deployment sometimes necessary. It wasn't a tag issue. At least none that I could see. Of course, the possibility exists that I could just very well be a dumbass. I just assumed that to be the Docker updates that have happened over the past year, and, without any new code, it just broke. There was a recent Docker/Portainer issue. It happens.

I either read somewhere or someone tipped me off to the fork. I can only speak for my network, but the fork did the trick. Have had zero issues, and I've been using it for a good while. Now, I notice that Watchtower fork hasn't been updated in 6 months. I guess it's either been abandoned again or there just hasn't been a need to do so.