I was going to mess with the new horses that came out and I just spawned a bunch of them using eggs.
What I expected to happen was a bunch of different types of horses would spawn that I could tame and ride around.
What actually happened was it spawned one adult horse and every other horse a baby horse. The babies followed the adult everywhere, but everywhere also meant within the walls and little ledges. I guess their ability to walk up a whole block is messing with their movement. It seemed to me that when the baby horses tried to jump a block, they were pushed back a little bit, like the block was an entity.
How to reproduce:
1. Find a hole with at least one wall.
2. Spawn an adult horse
3. Spawn a load of baby horses
4. Watch as they clip into the walls and take damage.