This is now a few weeks old, but I am just now getting to it:
I think I know what this mechanic is talking about, and I think I agree with him! As the window travels up and down, it wears out the rubber in FRONT of the window! I am sure that lubricating since new would have help with this wear, but it is too late for most of us now.
That wear gives window extra space to tilt forward and bind up! That binding eventually damages already poorly fitting regulator and white clips on the window.
Replacing the plastic clips with metal brackets and getting new regulator does not solve the original problem: split rubber channel with extra space! We need to ether replace the rubber guides (are they still available?) or build up some material for TIGHTER window fit (front to back).