Issues with redstone in 1.9

Piston wont grab the slime blocks back to where they were to cause them to stop the growth of the melons =<>ALSO IS AN ISSUE IN 1.9 JUST COULDNT PUT 1.9 IN AFFECT VERSIONS<>=

I expected it wouldnt do that and nothing bad would happen untill i noticed the slime blocks werent in the correct position

What actually happened was...:
Video --->> https://www.youtube.com/watch?v=K5le6wanbBI

Steps to Reproduce:
Watch the video to see it happen https://www.youtube.com/watch?v=K5le6wanbBI