Have the version 0.3.9 which gave one my players an NPE and Tesselating Block in World message. Prior to the crash it kept saying he was missing 3 ties and he was testing the mod in creative.

client crash report
https://pastebin.com/GnkiVe2d

There's probably a mod conflict causing this. I'll add a try/catch around here soon

Fixed the crash in 0.4.2