1911 hi capa parts

I can't get my We tech hi capa to cycle completely.

It has to either be the piston head/ o-ring or loading nozzle...i checked everything else...

I teflon taped the o ring on the piston head, so it has a tighter fit and it helped.. it loads a new round now, but doesn't go all the way back to lock it when the mag is out.. I'm positive its one of those two things...

So if you have any of those parts, i need them. This isn't my gun, and was bought used.