Rapidly placing and breaking redstone block and piston causes something weird.

Place and break a redstone block on top of a piston facing downwards results in the piston pushing the redstone block down.

 

How do reproduce:

1. Place a redstone block.
2. Place a piston (normal or sticky) facing downwards below the redstone block.
3. Constantly break and replace the redstone block with another redstone block.
4. The redstone block is underneath the piston.