While using my new blue Minior who I had taught Earthquake, Rock Slide, and Acrobatics, for no discernable reason during the second turn of a wild encounter the Minior forgot all these moves, leaving it just with Shell Smash, amusingly. This happened on two different Minior, one caught before this update, and one after; this bug happened twice to the new Minior. I have not yet experienced this happening with other Pokemon, so I have to wonder if it has anything to do with Minior, but I cannot say for certain. I don't have any ideas as to the cause.

After some additional testing, I thought it would have something to do with the transition between Meteor and Core form, but this doesn't seem to be the case. After messing around with other Pokemon as well, it definitely seems to be some sort of Minior-specific issue.

As far as the TMs used, of note is that the Earthquake TM was a Johto TM. I don't know if this would cause issues, but my other pokemon that had learned earthquake the same way did not seem affected.

https://clipchamp.com/watch/Ig8QGR2IOf0

It seems the bug doesn't necessarily have to trigger in battle, as I found it occurring some time between fleeing the battle with Timburr and using the Healer.

Greetings,

I can attribute this to Minior changing forms and having moves that isn't part of it's base moveset.
If you had checked the stats at the end of the battle, I bet it would have already forgotten everything but confuse ray.
In my testing, I did Shell Smash and Stealth Rock (moves it learns via leveling up) with Giga Impact and Charge Beam. At the end of the battle, it changed forms and lost both moves taught via TM.

Thanks for verifying - is this the sort of issue that would warrant a hotfix? It's up to y'all but it definitely sucks that I can't really use one of my favorite mons for now, would hate to have to wait until the next big update.