When a contraption made by pistons is operating the piston extender will disappear over a short time. The only way to make the piston extender show again is to reopen my world. I was able to confirm that this affects pistons in Minecraft Windows 10 edition.
To reproduce, Follow this video to create a simple flying machine.
- Give the flying machine you created sometime to move a certain distance from you.
- Fly over to where the flying machine has moved.
- You should now start noticing that the piston's extender is not showing. (Give it some time. the pistons will start to disappear and reappear again. Eventually they will disappear completely.)