The problem is present in the current version of the mod (chiseled-me-1.12-3.0.0.0-git-7c6a1ba)
The hitbox size for Metamorph transformations is increased in a way that it is always bigger than it should.
At sizes 8 or 16 the hitbox becomes big enough to cause a remarkable amount of lag.
In a previous revision (chiseled-me-1.12-3.0.0.0-git-3af10ac) where Metamorph hitboxes didn't increase/decrease in size the performance issues are not present.
The problem is present in the current version of the mod (chiseled-me-1.12-3.0.0.0-git-7c6a1ba) The hitbox size for Metamorph transformations is increased in a way that it is always bigger than it should. At sizes 8 or 16 the hitbox becomes big enough to cause a remarkable amount of lag. In a previous revision (chiseled-me-1.12-3.0.0.0-git-3af10ac) where Metamorph hitboxes didn't increase/decrease in size the performance issues are not present.