Way too many in use to call it a design problem. Surely construction or material failt.
In large general construction for about fifty years. In the recent years in the midwest i saw few failures due to skimping or shorting on the tradesman side. Many more design short comings or “changed conditions” such as underground obstructions or items not found in initial investigations by owner and designer.
I did see shoddy or poor workmanship but that was rejected outright and we are talking later failure.