My DA556 lower receiver mated with the Diemaco C8 upper went full auto at the range. Function test with RO's present proved perfect semi-auto only function, still went full auto regardless afterwards (even after borrowing another bolt assy.) Total round count since new on the lower is around 200. Individual part inspection revealed an unusual trigger reminiscent of full auto examples (with the open rear tang) came with my rifle, the parts would not function in another lower that was made in the US. I have since destroyed the Norinco FCG due to it's inability to transfer over to other receivers and the fact that despite manual function testing not showing full auto function, it would do so anyway when fired.
I've learned my lesson, the only redeeming part of Norinco AR's (to me) are the A1 upper receivers, the rest I cannot trust after my own personal experience. I also have a Norinco M305 that I have had nothing but good luck with, but despite it's value I'm still wary after my AR incident.