UPDATE: 09/21/2022, 2:25AM PST

So, I have formatted my entire system, and reinstalled the entire game. I backed up my character data via hard copy, and my system config data via server and hard data, and uploaded the back ups upon re-installation.

This entire process took me from 5pm PST to around 12am PST.
Upon getting logged back in and ensuring my layouts and configuration were fixed, I tried to edit my plate. It is now saving my changes, but this does not feel like a resolution to me. It should not take 7 hours of deleting and reinstalling data and programs (including others, not just this game, as I had no way of knowing if the game was at fault, free disk space, etc.) to make it so I can apply changes to my adventurer plate, just because I used a Fantasia which is awarded to each player upon completion of base-game.

I love this game. There's a reason I've spent so much time trying to resolve this. I am not condemning developers or anything of the sort, as I know they've got their hands full with some other (much larger) issues. However, I feel it needs to be made clear that the only solution that worked for me was 7 hours of moving, deleting, and reinstalling various files, programs, and other data, and that feels like a. Noticeable issue. And I feel it should be addressed.

This appears to be an issue only after the 6.2 patch according to other threads/comments about this concern, but another user said they had it happen to them without even using Fantasia. So it may not even be linked to that, it turns out.

My intent here is not to sound upset, or to place blame. It is only to provide as much information as I can in hopes of helping resolve this issue, so it hopefully does not affect more players than it (knowingly) already has.
I am glad I got mine working again, but frustrated that it took 7 hours and a system format to achieve, is all.

Hopefully this is seen and addressed. Again, I am happy to provide any additional information to the best of my ability, if it is needed.