Drivers Side Window won't close. on 2001 Volvo S80

Over the past 6 months, the window has been tempermental. Sometimes it goes down in one motion, other times it takes two or three depressions of the switch. This time it went down slowly and then I couldn't get the window to close completely, left approx 1/2 inch gap. It does not appear to be dropping uniformly.

Asked by for the 2001 Volvo S80