You might could try taking the switch out and cleaning it with alcohol.
The whole assy comes out rather easily. Once out, you can use a really small flat blade screwdriver to open the switch housing. Be careful taking to the cover off, because the window lock switch (on the lower part of the assy) will come out. No worrys if it does though, if you look carefully, you will see how it fits back into place.
Just try takeing alcohol and use a thin towel and run it through all the contact points of the switch.
