Sounds like the extractors are not holding the shell long enough for it to get to the ejector. Check the extractors to make sure they are working correctly, especially the one on the left side. The right side uses a coil spring and plunger to power the extractor and is pretty reliable. However, the left side uses a one piece extractor, the rear half of which is a leaf spring. If that spring breaks or looses tension you will have ejection problems.