Ford Sierra Saphire Window Problem

I have a Sierra Sapphire 1992. Niggling problem is that whilst for over a year the electric front windows have worked fine, today the passenger one would close but not reopen. Driver side works fine. I have checked the connections on the back of the switch and sprayed the switch and motor with WD40. But still no luck. Anything else I can check or try please? Don't want to buy a switch and the motor for the window is at fault or the other way around.
Thanks for any helpful suggestions.

check the rubber boots,between the pillars and the door.the wires are usually very tight and they have a tendency the fray and break,
either that or the switch could be fubared.
can you open and close said window from the drivers side ok?

Thanks for the ideas, I will check out the rubber boots,between the pillars and the door for frayed wires. (Friday I should have time).
There are just two switches for the front windows, one for each side. The connection positions are different, so cant swap them to try that.

I could not see a problem with the wiring near the door. But tried respraying the switches again with WD40 and it now works. Just hope it continues working!
Thank you for the ideas.