There could be several possible causes of glass breakage, including impact damage (deliberate or accident), edge damage (during handling), poor installation (tight glazing, missing setting blocks, proud fixings/hard surface contact with glass) and inclusions in the glass (foreign particles/impurities).

Regarding poor design, then insufficient clearances and structural movement can also lead to glass breakage. These should be sufficient clearance in accordance with guidance in standards and industry guidance, for example BS 6262 and GGF Datasheet 4.2. If there is structural movement of the building, which has not been accounted for in the design, this may result in glass deflecting beyond its limits and breaking. A twist being created by supporting arms which are not co-planar may also lead to glass breakage, if bolts are being used to fix the glass in position.

Only examination of the glass fragments (specifically, those around the origin of fracture) and inspection of the framing system and glazing method by an appropriate person is likely to determine the cause of failure.

If the glass has fractured, you should report this to the installer. If the installer is no longer trading, then you should consider approaching another installer to undertake the replacement work.