After some raging, I've finally found a possible solution though.
Atleast for me, the problem lies in the button that the scroll wheel presses and not the wheel. I found gets more prone to get stuck in a pressed position, which results in the scrollwheel not completely reaching the pressed-position of the button. To fix it, remove the cover and the the part that covers the internals with a T6 torx-screwdriver. Then first spray air around the button, which is under the scrollwheelshaft (on the right of the scrollwheel), with compressedair to remove potential dust. Then with a small plier grab the button from the side and pull it up with great force.
Put the mouse back together and the scrollwheel will work again, even when pressing slightly. I don't know yet how long this fix will work, since I have figured it out only yesterday. Sry for bad english i am from afriac.