Player entity randomly falls when standing on moving blocks

When player entities are standing on blocks moved by pistons, they may randomly fall through the floor when the piston is pushing blocks. It is more consistent when the player is pushed by a block from a piston as well.

To replicate

1. Use the machine shown in the pictures below
2. stand on the slime block, and press the button in the back
3. repeat and eventually the player should clip through the floor.

I apologize for the length of my previous report. I hope this helps in isolating this particular bug.