So I just finished the fix and the switch works again. However, I can report after a few weeks if it hasn’t reoccurred.
The guide of Koala Yummies
was of great value! So if anyone faces this issue in the future, please use his DIY on the previous page. If you open it up and see a yellow board instead of a green one (possible EU vs. US model), the I can share a few tips as an addition to Koala’s guide.
Below pictures show how the board in my CR-Z looks like. You can see the two grey boxes for the switch mechanics. In red, you see the part that gave me some trouble. On this black ‘stick’, the lock/unlock button for the windows is attached. You have to pull this button off before removing the board from the black plastic housing.
Next up, you can push and pull on the small black taps marked in red. On mine, the driver side one was way easier to move than the passenger side one. The driver sides one was the one causing issues in mine. So easier to slide means less friction, which means less contact, as will be seen later.
Now you have to open up the small grey box on the side that is causing issues on yours. You have to first push the LED a bit to the sight. Then you can open it by releasing the tabs on each side, marked in red. Please note that you can't fully take the top off!
On one side (not shown on the picture), it has metal pins along the side. So you can open it and bend the pins a bit to provide access to the slider inside.
Now get the slider out. This slider has three metal pins on the top and on the bottom. These six pins slide along metal strips in the grey box. I carefully bent these metal pins, as pictured below (sorry for the blurry picture). When putting everything back together, you can now feel that there is more friction when sliding the black tap on the side of the small grey box, thus making better/more contact.
For now, the issue is fixed. So hopefully it’s permanently fixed. If the issue reoccurs, I will post it here.