The game server crashes when a fireball hits a cherry boat. I am not sure if this also occurs with other boats from BYG, but it does not happen with vanilla boats.
Here is one of the typical crash logs that you'll get when you crash the server in this way: https://pastebin.com/Gn2YyqE1

ouch, I was a bit too quick to post an issue. The crash happens only when one of the other mods are installed. I'll try and figure out what's happening here and update the issue when I know what's happening.

The mod that's causing the crash is Twine, I'll see if I can open up an issue over there or submit a pr to fix it.