only a guess following net searches.
Minor damage during installation such as nicked or chipped edges which later develop into larger breaks
Binding of the glass in the frame causing stresses to develop as the glass expands and contracts due to thermal changes
Internal defects within the glass such as nickel sulfide inclusion. Its said the most common reason for these intrusions is when stainless-steel machinery is used in the manufacturing of the glass.
If you can contact the shower manufacturer ask who supplies the glazing for the enclosure explaning what's happened they may be interested and even offer to send a new door.
Bob
March 2013
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