Window switches
I have had a couple of instances of sticking electric windows. In the course of investigation I dismantled a couple of the switches, and cleaned the contacts and connectors. I found them to come apart quite well so below is a sequence of pictures showing strip-down of a switch. These things are plastic with small springy bits of metal which will leap off into the darkest recesses of the shed if you let them. Take care and use a large clean work area, not the lawn.
Below, 2 possible ways to get the contacts out. I preferred the second, lever the spring a bit from behind and lift the outer with a thumbnail.
With all the contacts out and accessible, I had good results cleaning the blackened bits using an electrical contact cleaner. I applied it with a stick of balsa which worked well. One of the springs was a bit soggy and lacking in "snap", it was gently bent down and squashed for more length.
Note the switches are polarised into the connectors, two corners have bevels on them. They will however fit either way into the housings, so try the switch first to get the window going up/down in your preferred switch direction.
Aixam