You ever randomly crash for no reason?
Is "Embeddium", "Rubidium", or whatever Sodium variant we're using now always listed as the cause, even though removing it doesn't fix anything?
Does the crash report say things like:
Then this will be a band-aid slapped on the issue!
Yeah so I don't know what's actually causing it, but somehow there's a block present on the server that isn't present on the client, so when the server says "alrighty Client, sending you another chunk!" the client goes "Server, I don't recognize this block ID. I'll handle this in a responsible manner and OH GOD OH F***" and crashes the game, sometimes even crashing to desktop through NotEnoughCrashes.
Just add this to your mods folder, and it'll make those pesky "unknown blocks" look like dragon eggs instead. Because those were the most noticeable blocks I could think of. This is so you can use the /setblock command to remove that unknown block from the world and fix the game for people who don't have it installed.
It's a bit of a janky fix, but in lieu of actually being able to figure out what the heck is causing it (which is really difficult because the whole chunk is stored as binary data so it's tough to find which exact block position is crashing the game), this will keep your game stable enough to keep playing.
