When a block that the player is standing on is moved a moving block will appear in it's destination instantly. However the player is moved half a block at a time, twice. This allows the player to fall through the block, which is bad for players who want to stand on flying machines.

I would expect the player to move with the moving block so they don't fall off. This may cause some visual issues though because the animation for moving blocks is aligned to how the player moves. It may make sense for moving blocks to be changed instead (without making them fully solid).

Steps to reproduce:

1. place a sticky piston and power it
2. place a full block on the face of the sticky piston
3. move as far away from the sticky piston while crouching on the block (be carful not to go over the edge or you won't get moved because of a different bug)
4. retract the sticky piston
5. you'll fall through after being moved half a block

I slowed the game down and then created a quick video demonstrating the bug.

If you crouch over the edge of a block you will not get pulled either, but that's not because of this bug.