Pistons randomly not working


I've got a strange bug which makes some pistons not reacting.
The thing about it is that they are almost completely randomly not responding. If they do actually respond, they'll do it for the rest of the 'playing time' . When I'm giving it a new try by switching to playing mode once again the selection seems to shuffle, leaving me sometimes with properly working pistons.
However, there are pistons that do not show this behaviour and always hammer the sh*t out of dem farmers if I want them to do, though i have not figured the conditions out yet.

Windows 7
Newest version, steam says BuildID 6999091

Intel i5-750
Radeon HD 4890



Attached Files
This is a well known bug, detailed by at least 30 bug reports in the bugs list highlighted in red at the top of the bug report subforum.