When placing an item frame on top of a fence gate, It won't let you place it on top of a closed one, only an open one. If you place it on the open one then close the fence gate it breaks off.

I found this when creating a void room with redstone over/under door to trap members inside, 

I would expect the item frame to stay on top, regardless of the fence being opening or closed, and not pop off, and also that is should let me place it down when the fence is closed as well.

Here is a video of what is happening: https://www.youtube.com/watch?v=jWG4vWI-9wU