"ghost" blocks appear when pistons move on automated farms

Put the summary of the bug you're having here

What I expected to happen was...:
With this farm all it does is uses hoppers to make a clock that breaks melons when ever they grow just a standard melon/pumpkin farm

What actually happened was...:
about 3/7 times the pistons fire the block connected to my sticky pistons duplicates and moves the glass surrounding my farm the block duplicates and moves the block further and further away the image i provided shows the moved blocks (also happens on my sugarcane farm) but when i break the duplicated block nothing is dropped

Steps to Reproduce:
1. create an automated farm using a hopper clock and sticky pistons