Duncan:
I'm sure you know all of this, but here are my thoughts after reading your post.
The determining factor in diagnosing whether a problem such as the one you describe is a failure-to-eject or a failure-to-extract is the nature of the clearing action required to overcome the malfunction. If the fired case can be cleared by simply racking the slide, a failure-to-eject has usually occurred; if repeated racking cycles are needed or if tools are required to clear the malfunction, then you're dealing with a failure-to-extract.
Ejection failures in a semi-automatic weapon are often related to a damaged extractor, a weak extractor spring or, much less commonly, to a weak or damaged ejector mechanism. Failures to eject can also be caused by an accumulation of carbon or fouling on the extractor or the ejector mechanism, and from short or defective recoil. You indicate that you had carefully cleaned the pistol before the range session. If repetitive malfunctions occur which are not corrected by cleaning/lubricating and do not appear to be ammo related, you may have a damaged extractor, extractor spring, or extractor roll pin. Much less likely, but still possible, would be a damanged ejector mechanism. All of that having been said, however, my long-distance suggestion is that the problem with your R9 might be due to a weakened recoil spring which is adversely affecting recoil cycles and resulting in failures to extract and eject spent cartridges.
Good luck!
