Animals able to escape fenced areas

When I go out to breed my cows and sheep they seem to be less and less in the fenced area and more around my house. i have seen it happened to the point where the other cows simply pushed the cow out, but instead of glitching back in it walked around outside the fence and went to my house. You can re-perform this bug by spawning or luring cows or sheep into a fenced area and waiting/watching.