Detector rail duplication glitch

Put the summary of the bug you're having here

What I expected to happen was...:

The Rail Break and drop just 1

What actually happened was...:

The Rail Break and dropped 2

Steps to Reproduce:
1. Create rail made of 3 consecutives detector rails
2. Put a minecraft in the central one
3. break a block next to the central rail

4. Put a stick piston next to the broken block and then power and unpower it

PS:There is a video of how it works and also a screenshot of the setup