Machining can be bad regardless of the rods. There are lots of bits to be machined in an engine and it is far more likely that there will be an error there before a rod breaks.

Anyone can attempt to build an engine either with or without steel rods, so there could easily be a mistake made.

Det can be caused by many things. Fuel Pump failure, clogged Fuel Filter, fuel starvation caused by cornering too hard, badly set up, too much boost, compression too high etc etc etc.