Weird Error when trying to play dungeons on 1.20.4 - doesn't allow players to enter.

Hmm... this looks like some sort of issue with the dungeon map itself. Are other dungeon maps working fine? What's the dimension type? (Overworld, nether, end, etc.) I can't seem to replicate it...

This error seemed to be an issue with MyWorlds in some capacity. The person was using MyWorlds and the worlds weren’t loading correctly. It was fixed by manually loading the worlds back into memory once.