Title says it all. If you light something on fire and look just a little bit over it the fire animation will stop rendering.

I searched for this before I posted by the way.

How to reproduce:
Set something on fire. A creeper will work fine.
While it's burning, look up over its head slowly until you can barely see the top of its head.
After you look far enough, the fire animation will stop but the creeper will still be taking damage.