On a multiplayer server(1.16.4),me and my friend have had this issue we are unable to fix. We were able to play the server perfectly fine. For my friend, she got onto an elephant from another mod and triggered this error code
'The game crashed whilst unexpected error
Error: java.lang.NullPointerException: Registry Object not present: hudcompass:xmwaypoints
Exit Code: -1'
We couldn't fix it and had to start a new server.
For me, I used Xaeros Minimap and made a waypoint for the first time and it also triggered this code. I have the mods in and it won't fix. I am able to join before getting kicked immediately and crashing.

No matter where I look, I can't seem to fix this issue.

Thanks for the report, I'll investigate.
Is there any chance your configs were corrupted?

Uhmmm, I'm not sure. I managed to fix it by getting rid of the mod but I can send a thing of the crash reports