You are reffering to the stripping at the edge of the door, not the trim where the window slides into, right? Mine wrinkles pretty bad and I have to push it towards the front to straighten it out pretty much every 4 times I use the door. Can any of you (who have this problem) tell me if you're door doesn't shut softly/properly anymore? My door usually doesn't shut on the first try unless I really slam it. Typical of aging 2-door vehicles. Anyway, on my car, this is due to the lower door hinge being cracked and so the door is not aligned properly anymore causing the stripping to rub or slide against the inner door panel when I shut the door. Maybe this is a common problem so check out those hinges!
Ahh. Wait a minute. The heading says "Glass run channel" I'm a dumbass. Sorry. This still could be helpful though.