Slime blocks might not get pulled by sticky pistons.

Slimeblocks seem to not get pulled by sticky pistons in certain situations.

Think it is probably easier to explain the problem with a video:
https://www.youtube.com/watch?v=NOgBDMZfvVQ

Also, this setup (all three pistons are sticky), the button on the blue wool will drop the slime block while the red wool-button will work as expected.

http://imgur.com/u7AovLc

So I guess it has something to do in which order the pistons are activated, maybe.