Warning: World created from an incompatible version

I wanted to log in to my Survival World from 1.18 experimental snapshot 6, but it said that world was created by an incompatible version. It was supposed to be compatible, since it is also a development version of 1.18. What do I do? I also found a bug where if it says to back up a new world, it doesn't let you do that. It doesn't even let me re-create that world, either. Please see MC-236742.