World not loading glitching mobs/animals

I was playing after getting out of the Nether (I had just built a portal) and I came out and part of the world wasn't loaded and I walked over there. First a pig started glitching. It was moving it's body side to side (along with it's head) over and over. Then a few mins (2 creepers and 1 skeleton) did the same. They got frozen in that area glitching. Nothing else was frozen and everything else was loaded in.