I had 4 pens one of pigs, one of cows, one of chickens, and one of sheep. None of the pens were cramped there was a lot of space for each animal. But all of the animals kept glitching through the fences. It happened the most with chickens and pigs but it also happened a lot with sheep, it was very minimal with the cows.

Sorry if this doesn't make sense I haven't made a proper bug report before.