Versions

Betweenlands version:

3.2.1-alpha-snapshot-universal

Forge version:

1.12.2-14.23.1.2604

Singleplayer or Multiplayer:

Singleplayer

Installed mods:

1. The Betweenlands
2. Valkyrien Warfare (version 1.12.2-v0.9_alpha-full)(build 129)
   Also can be reproduced using the curseforge release.

Link to full crash log

https://gist.github.com/RFShahrear/1fc910ab5ea8d67e472b97ae6ca292ad

contains both server and client log, along with the crash report

Description of the problem

How to reproduce:

1. Create a ship
2. Go till a chunk unloads.
3. wait while the ship jumps around crazily (you can't get off the ship at this state), before crashing

We just released v3.0.0 (https://minecraft.curseforge.com/projects/angry-pixel-the-betweenlands-mod/files/2529098) which removes that crash and made it a warning in the log instead. Please try with that new version

Talk about timing. Yes, it seems to be working fine now. Thank you very much.

Hehe yeah, it was minutes apart :P
Glad it's fixed.