Fakename not changing 1.18

[vonist]

Hi, I just recently downgraded my server's mods to 1.18.2 from 1.19.2. This error is just now occuring.

The player is changing their name and it changes in tablist and overhead, but not in chat or death messages. I've tried clearing their name and resetting it, I've tried reinstalling the mod, and I've even looked in player's NBT files. Even without the mod on the server, their name in chat is STUCK as a previous set fakename.
I'm unsure how to recreate this, but there is 2 people on my server with this error.
I've tried deleting player's data, that didn't change anything either.