Put the summary of the bug you're having here

What I expected to happen was...:
Made a pen of fences. To keep animals in.

What actually happened was...:
Animals are crowding together in a corner of the pen and pushing/glitching one another thru the fencing.

Steps to Reproduce:
1. Make a pen.
2. Capture any domestic animal.
3. Breed and sit back and watch or come back to notice that some of them are not in their respective pens no more.