Player tick update procedures which grant advancements prevent players from connecting to server.

I have no idea why, but for some reason when I create a player tick update procedure which grants an advancement, it works fine in singleplayer. But when I get my friend on and play on a server, it disconnects the target player and prevents them from joining unless they no longer have the effect/are near the entity which causes the advancement to be granted.

There is no crash log because of the server not crashing, but I have the latest.log which shows what happens when the players disconnect.

the log

I noticed that it says Caused by: java.lang.NullPointerException: Cannot invoke "net.minecraft.advancements.Advancement.m_138325_()" because "p_135986_" is null, but I have no idea what to do with that information. Any help is greatly appreciated.