Put the summary of the bug you're having here

What I expected to happen was...:
The piston to retract and the Redstone to stay on top of the piston.

What actually happened was...:
after the Redstone signal was deactivated and the pistons retracted, the Redstone on top of the piston broke

Steps to Reproduce:
1. Place Redstone on top of the piston (Piston facing down), activate the dust. Then turn off the signall

EDIT: After testing more this is also true for repeaters