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.

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And then I reopened the game and the issue was gone

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Fourth image happened when I filled some stone and grass just now in that flat map.
Reopen the game can solve the issue too.