Just in case anyone else has this issue. Most will not see it unless you are creating a bunch of custom mobs. If the default initial state is set to 0, which is what the default value us, you will have issues. Always set your spawns for initial state 16516 or the mobs will either be above or below ground when they start to roam on their path.

I am so glad I posted this, slipped my mind and ran into the same thing.