I reported a separate issue with not being able to place my armor on the Armor Stand. While trying different things to see if I can get it to work, I noticed that if I have a piece of armor in my hand and I hold right-click for a few seconds, it equips the piece of armor. After doing this, I can't remove the armor. When I click the armor, it looks like it quickly moves to my mouse location and then back into the armor slot. If I shift click on the armor piece, it moves into my inventory and then gets equipped immediately. If I save and exit, and reload my game, I can remove the armor without issue.