The mystery of the open right mag has been solved. I bought two Bogert P-leads from Aircraft Spruce and one of the adapters was too short to extend into the well and make contact with the spring finger down there. I'm not sure whether it was a manufacturing error or just needed adjustment but for now, I just adjusted it. If anybody cares, the depth of the hole in my Bendix hex-nut mags is 1.03". I adjusted the length of these adapters to be .02"-.05" longer to apply some pressure on the spring finger as the hex nut is tightened. This just seemed the proper way to do it, but if there's an official specification, I'd like to know.

So now both mags are back on the aircraft and timed and the crankshaft oil seal has been replaced. So after almost two months of down time to incorporate ADs on the engine, she should come back to life next week.

As received, the adapter on top was adjusted down to the bottom of the plastic threads and was too short to reach the spring finger in the mag:



You can see the slight gap I left between the aluminum cylinder and the mag to apply pressure on the spring finger when the hex nut was tightened: