This particular break may have been from poor casting, but these tripods should all have a retainer built into them like the Meade field tripods to stop the legs spreading too far and straining the hub - poor design.
I know of one other tripod that broke in the same spot. Apart from extending the legs too hard and straining the connection to the hub, the bolts can be over-tightened putting strain in the other direction. I treat my tripod carefully to try to avoid such a breakage.
