I've noticed that custom wolf mobs have a glitch in the tail animation. Normal wolves work fine, but for some reason, custom variants have a windmill effect to their tail. By this I mean that the tail constantly spins forward like a paddlewheel boat, clipping through the wolf's back. Taming has no effect on the spin.
I'm not actually sure if this is an issue with MCreator or the Minecraft Forge client, but in either case it is extremely annoying.