When riding a mob, clipping your head into a slab makes black bars

While riding a happy ghast and clipping your head into any slab, large black bars cover the portions of the texture a second slab would go onto

How to replicate

1. Trap a fully grown happy ghast in a four by four box (interior size)

2. Make the top of the box out of bottom half slabs (this happened to me with waxed cut copper slabs)

3. Attach a harness to it

4. Ride on top of the ghast

I am unsure if this works with other rideable entities but know it’s repeatable with the happy ghast.