[Forge 1.20.1, Version 1.9.10] Per player difficulty not working.

[ScrubbyCoding]

Per player difficulty still appears to not be working. In the meantime, does anyone know the last version it might have worked on? Also, when running the gamestage command to check an individual player's stage, the command says an internal server error has occured. I'm going to assume these issues are related. When I checked the majrusz's difficulty mod's .dat file in found within the server's world folder, the section for "player_game_stages" has 0 entries, implying its not even recording the progression of the player's individually. I have tried a lot of things to get this to work, including deleting the .dat file, the config, and the mod itself.