Summary:
Falling blocks such as sand will break when falling above a vertical retracting sticky piston.

Steps to Reproduce:

1. Place a sticky piston facing upwards with >1 block of sand on top of it.
2. Provide redstone signal to sticky piston to push stack of sand upward.
3. Turn off redstone signal to retract sticky piston.

Observed Results:

1 block of sand from the stack will break from the fall.

Expected Results:
I expected the sand to fall and land as a block, not drop as an item. This works with normal pistons but with sticky pistons the sand breaks. This also occurs if there is another (non-gravity) block between the sticky piston and the sand. I discovered the issue when trying to build a 3x3 sand door using a vertical triple extending piston.

Screenshots/Videos attached: No