[jsb5717]

That's how tempered glass breaks...a safety thing. I've been in the window business for 35 years and have seen a lot of tempered glass break. There are several reasons why it could break. Anywhere from a manufacturing defect that allows something sharp to remain in contact with the glass to just hitting it too hard with something while traveling and it eventually gave way. It could be the constant pulling on the attached travel catch. Too much stress at that point could do it. Or, heaven forbid, you forgot to latch it before your last travel.

Hard to say what got it. Fortunately you've got the warranty.