bump....

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

Pretty late on this thread. I believe your problem would be in the rubber seals. The felt like covering is wearing off. I have found that 3M makes a silicone paste that fixxes this problem for about a year.

I think I found the source of the "tightness" The guide-rails don't seem to be parallel where the glass mounted brackets slide.As the window went up past halfway the brackets were bottoming out on the rails and dragging. I pulled the brackets off one at a time and cleaned the sludge that was white grease off.I found remnants of a silicone grease inside the brackets so that's what I used when I put it back together (Sil-glyde).I adjusted the brackets in a hair and the problem seems solved

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight