Have you had it all the way apart? Any obvious burrs on the sear or disconnector? Sear spring have all 3 fingers? Does your trigger have a overtravel screw? If so, have you tried it without the screw installed?
It does sound like the disconnector is sticking. Check the half-moon cut in the bottom of the slide, it may be filled with crud, preventing disconnector from travelling fully upward. The other place I'd look would be the trigger bow.
Its a Springfield National Match.
I have several types of mags but I mainly use Chip Mc Cormicks.
The original mag is the only one that it does not seem to happen with.
I have some Wilsons ( I think ) but they will not eject from the gun.
I am thinking about looking into the mag release and or the trigger bow......