Put the summary of the bug you're having here

What I expected to happen was...:
I thought that the pistons were going to retract after I pressed the button to collect my sugar cane.

What actually happened was...:
Once I pressed the button, It collected my sugar cane just fine. But when the pistons retracted, the top row of pistons appeared retracted but an arm was still sticking out there. This counted as a block so the sugar cane couldn't grow to its full height. It is a waste of durability and time to have to go back through and break all the weird piston arms every time I harvest. Also, they only stay extended when the sugar cane is at full height.

Steps to Reproduce:
I have all the redstone wiring and my set up in the pictures below.