Disappearing honey blocks

So I was just testing out some flying machines, and found a model in which one of the honey blocks constantly keeps disappearing and reappearing! If you stand on it it will push you under. I have no clue why it is doing this.

Steps to reproduce:

1. To make the flying machine, place down two honey blocks horizontally adjacent to each other. Behind the honey blocks on the left side, place a sticky piston facing towards you. In front of the honey blocks on the left side, place an observer facing towards the left. In front on the right side, place a piston facing away from you. Then place a redstone block behind on the right side.
2. stand back and watch