MoCreatures and Morph Mod (only two mods in my server) crash on start due to ticking an entity that's usually an aquatic creature- in my case, it's a Cod; entity from Mocreatures. I've already contacted the mod author of Mocreatures and I am awaiting a response from them, but I'm also posting an issue here in the meantime.

In MoCreature's unofficial Discord, i also asked about it and was told this after they observed the crash report:
the first cause is a mod conflict in which MoCreatures is expecting the mob entities 16th parameter to be true/false 1/0, the second cause is another mod using the 16th entry to store something of it's own. They said "there is no fix for that right now as it's hard coded into both mods", but I don't know much Java myself, so I don't know if there's some possibility of that being fixed.

They said another cause is that another mod is spawning creatures using it's own code (bypassing custom mod spawner) which results in that 16th entry being initialized/random (something they're trying to fix in code).

I'll also add that this crash doesn't happen in Singleplayer, only when i'm in a Multiplayer server.. don't know the reason.
crash-2020-11-13_16.58.24-client.txt

As Morph has just been rewritten and released for MC 1.16.5, I am clearing the issue tracker as I have not provided any support Morph for 1.12.2 and earlier. My apologies for not addressing your issue.