When I put my render distance to 5 and up the world freaks out and keeps changing. It seems to only be graphically because I can't interact with the blocks that keep changing, but I can interact with the blocks that were there before. It changes whenever I move. Also there seemed to be a huge mob that moved in one part, but it was hard to see and I can't tell what it is.
https://www.youtube.com/watch?v=MygkC8SJ9UE