When trying to place piston diagonally to the redstone block it can sometimes spawn these "double pistons"

Steps to Reproduce:
1. Place a redstone block one block in the air
2.  While moving right while looking at the redstone block direction place a piston and it will sometimes spawn these strange things

3. After you spawned a double piston, you can break redstone block and piston base block (not the extender)

How to delete:

1. Try to place any block at the remaining piston extender, it will vanish.

These bugged piston extenders cant be broken and always replace when trying to break.