I was just browsing the forum & came across this thread. I think I can offer an explanation for the exploding sun roofs.
I have been in the commercial building glass industry for 20+ years so I have learnt a thing or two.
The breakages are probably caused by nikel sulphide inclusion (NiS).
This is an extract from link below.....
"Over a certain period of time NiS will slowly convert to the original low temperature structure. This means the NiS increases in size, and the mechanical stresses caused by this cause the tempered pane to shatter, for no apparent reason (hence spontaneous glass breakage)."
I hope this helps.