Out of square new vinyl window sashes:

Several of the sashes in some new double hung vinyl windows came with sashes that were out of square.

The Milgard service rep reworked these sashes on site and squared them up.  I think that he used a heat gun, but I don’t know the exact procedure that he used.

Now, a couple of weeks later, two of the sashes that he worked on have a crack that starts at the sash frame and runs about 7″ into the glass where the crack just stops in the middle of the pane of glass.  One crack is in the exterior pane of glass and the other one is in the interior pane of glass.

I can’t think of any way that any of the activities on site could have caused cracks like these.

I’m wondering if stresses were caused when the sashes were squared up that may have caused the glass to crack like this when the temperature changed?

Does anyone have any experience with a situation like this?

Does anyone know of a window industry website where I could get technical feedback on this issue?

I’ll need something to back me up when I argue with the window manufacturer about this.

THANKS!

Bill D