"The game crashed whilst ticking player
Error: java.lang.IllegalArgumentException: The synced data key cgm:aiming for minecraft:player is not registered!
Exit-Code: -1"
Full Crash Log here:
https://pastebin.com/HFM2f4yA

Duplicate of #241

Just to summerize, this has been an issue for a while now. I've been struggling to create a fix since it's not as simple as it seems.

Have had this issue too, where it is unable to sync cgm:aiming for some reason.

same here, making a new world is often fine, but loading a saved world is where i crash.. but it worked on my server?