My side windows were blocking when trying to wind up. I always had to pull the rear part of the window up a bit by hand when winding it up (the windows where hanging down on the rear side).

I opened the inner door panels and found this nice mechanism (see image). After some try and error I found that it is very simple to fix the problem: you can loosen the screw (marked yellow) and move the window up a bit on the pulling cable and then tighten the screw again.