I tried grappling a Cachalot Whale with a diamond hook from the Grapple Hooks mod (https://www.curseforge.com/minecraft/mc-mods/grapple-hooks) and it crashes my game.
The launchers says this:

The game crashed whilst unexpected error
Error: java.lang.ClassCastException: com.github.alexthe666.alexsmobs.entity.EntityCachalotPart cannot be cast to com.github.alexthe666.alexsmobs.entity.EntityCachalotWhale
Exit Code: -1

Here is the crash report:
crash-2021-09-05_16.19.35-client.txt

I am playing on 1.16.5 with version 1.12.0