Can't add much to what Wally said. Could be a combination of a too strong striker spring and a weak return spring. The MK I return spring? in the pic was replaced by a double spring in all Mks. I had an old MkI spring and had to replace it with the double spring. The semi's can be made to run on gas setting 3 or 4 but for best reliability the holes should be opened up since you are compressing an additional spring in the semi set up.
Looking back at your pics. the first thing i would question is the striker spring setup. Looks way too stiff. I've built semis with a striker spring in that location but it was much smaller and just slipped over the return rod , went back in the return rod hole and cocked the striker on the bolt return.
Thread on resizing gas system:
https://www.milsurps.com/showthread.php?t=45105
Good Luck
Joe