A block can be placed where an Item Frame is occupying producing strange behavior.
What I thought might happen: The Item Frame would brake instantly or block wont be placed.
What actually happened: The item frame popped put of the block.
Note: It might also be left intact if block was immediately removed
Steps to Reproduce:
1. Place Item Frame on a wall
2. Place a block in the space the item frame is occupying
3. Either immediately remove the block (Item Frame and contents will be left intact)...
4. ...Or wait for 2-5 secs and Item Frame and contents will pop out in a random direction
The reason a block can be placed is because item frames are treated as entities.
For now, I'm assuming that it is intended behavior.