Model rendering bug

First image happened when I got into a 15w31a map.
Second image happened when I created a new flat map after delete the 15w31a map.
Third image was the same as the Second,in 3P camera.

And then I reopened the game and the issue was gone

Fourth image happened when I filled some stone and grass just now in that flat map.

Reopen the game can solve the issue too.