Glossy Dreckos eventually stuck on one tile

I had run that stable for a long time without issue, it seems with the fast friends update that the glossy dreckos that eventually roam to the rightmost edge of the stable as seen in the screenshot. They got stuck, I had to wrangle them, putting in another spot in the stable, they start roaming, but eventually if they arrive at that same edge they're stuck again. I deconstructed that tile, but then they're stuck to the next rightmost tile.