For what reason did the glass door suddenly break?
Yes, we had that happen years ago. It looks like spontaneous failure due to nickel sulfate inclusion. It happens in about 2% of all doors, is a material defect and therefore is actually a warranty case. But it would be hard to prove.
We were lucky at the time that the door was completely cracked, but it stayed cracked long enough for me to take a picture. And the photo shows that the cracks appeared somewhere in the middle of the door, so it wasn't a bump or anything like that.