See EnigmaticaModpacks/Enigmatica6#2307

Original poster was playing on Enigmatica 6's server, which if I'm not mistaken has the 3.9.2 version of Tetra and 1.9.1 of Alex's Mobs. The official server also has Lithium (presumably a forge port that isn't on curse yet) installed, so that may be a factor.

Use the bug report template in the future.

Closing, duplicate of #422.