Animals get stuck in blocks

Animals keep getting stuck in my plaza stone. This is the third herd to get stuck in this same spot. Before it was cows, then sheep, now goats (so I know it's not the animal type.) I picked away the blocks to set them free, but they walk a step and get stuck again. The area is 2 blocks high of stone with a half block step around it. They always get stuck near the step. I've now replaced that area with a different type of material, this time marble, to see if I get the same result.

Any advice?

They get stuck inside the blocks. Oftentimes they flicker in their attempt to pick up their feet and walk farther. I have managed to destroy the blocks so they can walk another step, but they just get stuck in the next one.

I've done a few adjustments to nail this error down. My guess is that they can't get up the half-block step I had, but I can't confirm that yet. I've replaced the half-step with a stair-shaped block, and no one has gotten stuck on the plaza top yet, but I can't confirm anyone has wandered by to try. I tried to herd them towards the plaza by shooting the gun to get them to run, but I guess I'm not much of a cowboy as I can't get them to run in the direction I want.

Another hint seeps that these cows walked through a full block set into the ground, but these *don't* get stuck. It was only they when they were on top of my plaza.

I've built a little test plaza in a place they like to congregate and will watch and see what I can figure out. More soon.