"Chopping" the back plastic window everytime you lower it?

[CA_Boxster]

I had the same experience where my plastic window cracked a little at the top center. I bought it used, but I assume the original owner didn't do any chopping. The dealer also told me that they wouldn't cover it because the window had not been trained properly to fold. This seems to be a common problem. I was told by the dealer and by an independent shop that, if the chop is done from the outset, after a while the plastic "remembers" how to fold correctly.

I tried training my 4 year old window to fold correctly last summer. It did start doing it, but only when the plastic was warm. Right now it's back to creasing the window in the top center.