Piston appears to be retracted AND extended when rapidly changing the signal strength

Okay, here's how to reproduce:
1. Build the circuit in the first screenshot
2. Place redstone block on purple part
3. Watch the piston with the light blue wool rapidly flash between the states in the second and third screenshot
I think this is due to the fact that the signal strength is rapidly changing, and for a short while the piston may actually have no power, I cannot be sure on that though.