Under some unknown conditions, Udon does not call Start and Update on specific udon behaviours.
The behaviors in question at at path:
Everything/MainRoom/MahjongRoot/MahjongSystem/PlayerPosition [1-4]/PlayerTileArea
Clicking the Sort button should arrange tiles immediately in front of you via this UB; however, because Start and Update are not being invoked, this fails to make any progress. I've added debug logging called on start ("=== TileSorter: Start()") to demonstrate that this is in fact not being called.
I unfortunately do not have a minimal repro as I do not know what conditions trigger this - it began happening when I switched some of the UdonBehaviours in the world to None sync type, but that does not explain why Start/Update might fail.
This may be related to https://feedback.vrchat.com/vrchat-udon-closed-alpha-bugs/p/owner-information-is-not-correctly-synced-to-new-players-when-there-are-many-udo (which reported a similar phenomenon as an aside). I'm not sure if I have objects being disabled on start (but I guess I have to go looking now...)