My back window is looking ghastly!!!

[polkfarmboy]

Well here is the story, 3 weeks ago I went to a DIY car wash and when I rolled down the top the back window stitching ripped a little at the top. One other time I went to put the top down and it ripped more, went back to the same car wash today and it ripped again so now from the top and half way round each side leaving 50% stitched.

Is there a problem with these plastic windows in the sunlight getting warped or shrinking because it gets worse when I wash the car.

I need a fix for this and the car is a 99 so I may look into glass if you can use any years model of boxsters rear glass window.