Sounds like one or both of the clips broke. That would allow the glass to move and grab some grease causing that smudge as it goes up and down.

These things.





Could be in combination with a regulator slider failing. Full failure of that though drops the window glass into the door. If you're in the door doing the clips... replace the slider as well and add a zip tie around the part that holds the cable. You'll never have problems again. At least not with that particular window.

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