I have run into an issue regarding pistons and gravity-affected blocks. It requires the gravity-affected block to be placed on another block that is in a position that allows it to be moved by a piston so that the gravity-affected block no longer has a block under it after the piston fires. (This can easily be modeled by having the block that is being moved in a position where it can be retracted by a sticky piston, as shown in the attached video.) I would assume the gravity-affected block would simply fall after the block under it moves away, but it actually gets destroyed. I have also tested this with just the piston head moving instead of the full block, and it appears that this bug does not apply in that case.