Insert an empty magazine and open the slide while watching the followers interaction with the slide stop lug. You should be able to see what is going on to keep the slide from locking back on an empty mag. You can also see if it will lock back on an empty mag with hand cycling slowly to see if it is possible that the follower isnt getting the slide lock pushed up before the slide starts going back into battery. I would also make sure the slide lock moves smoothly through its range of motion with the slide held back.
I would suggest potential failure points to be one of the following.
The magazine follower isnt making sufficient contact with the slide lock lug to push it up.
The slide lock cant move freely through its range of motion and magazine spring cant overcome the resistance.
The slide may be moving too fast for the slide lock to be pushed up in time to catch it.
The slide may not be moving far enough to the rear for the slide lock to engage the notch.
Just my thoughts on what I would start looking at if it were mine. I am definitely no professional though.
I appreciate the response! I watched a couple of Youtube vids on this particular issue. Apparently, I'm not the only one (imagine that)!
One vid suggested switching to Wilson Combat mags (at $50 each), the other vid was a gunsmith that actually diagnosed the problem that the slide lock lug is not making sufficient contact to the mag due to a cheap cast part used by Springfield. His suggestion was to buy a $20 slide stop from Wilson Combat to replace the factory POS part. I am going to look the 1911 over closely tonight and I will probably go with replacing the slide stop first to see if that helps.