Ok, so here's my problem. I have a pretty large above-ground sheep farm, with 3 high fences. About every time I log on, i notice about 3 of my sheep are wondering around my residence (Their not glitching because I have to eggify them to get them back in my farm)! It's getting really annoying having to put sheep back in my farm. Any ideas?
Build it one below ground but cover the top. Have a space of four blocks between the grass and top. You can see an example of my pastures at 8939 on smp4.
Animal glitching is a known issue. Instead of making the animal den above ground, try "burying" your animals, with a wall of at least 2 blocks thick, this works well for me.