The bug

When using `/tick step 1`, moving blocks have a random chance of being 1 tick behind depending on your connection. To reproduce:

1. Run `/tick freeze`
2. Power a piston
3. Run `/tick step 1`
4. At this point, the piston head could either move forward half a block or stay in its initial position.

Serverside, the piston always moves forward half a block.

Case where it moves forward on the client:

Case where it does not move on the client: