I played on a server for 5 hours, and it worked perfectly, but once I made a flintlock musket the game freezes and I got kicked out of the server and couldn't join back. I tried doing the same on a LAN server and this time the game crashes. I never experienced this bug on single player.
Note: While I couldn't join the server back, every one on the server had no issues, same with the server.

What version of the mod and MC were you using? Do you have a crash log you can attach as well? That will give the info needed to start debugging.

The version was 1.18.2 oh and the game crashes on singleplayer too.