Howdy,
I have been struggling with one that extracted cases but left them in the gun and I seem to have it worked out.
Here is what I found and things you might check.
The ejector pops up from a depressed posistion between shots and if dragging can miss the case being pulled from the chamber. I dressed mine with a stone and replaced the spring.
Build up under the extractor can be a problem. It was not mine, but I watched a fellow shooter's reliable 52 melt down and stay unreliable untill he pulled the extractor and removed debris.
Mine boiled down to a weak extractor spring. I would slow cycle the gun and it would work but cases bounced or dribbled over the ejection port. If I would cycle it fast I would encounter the condition thats shows when shooting it. I replaced the spring behind the extrator and the gun runs and can be cycled by hand and the brass flies out like it should.
These things wont cure everyone's ills but I hope they can help someone.
Thanks and good luck

Mike