So I created a new world in the latest pre-release, but when I tried to load it later, I was greeted with this screen:

My world was NOT saved with experimental features. To test this, I created another new world, exited and saved, loaded it up, and the exact same screen appeared. Whenever I try to create a backup and load, the game crashes. However, "I know what I'm doing" loads the world up as normal. What's going on? I didn't have this problem in 20w22b or any other previous snapshot prior.