If you are shooting full power loads and if your gun has the older style short ejector, and if you are using a standard weight recoil and hammer spring, it sounds like you need to either remove the shock buff or install an extended ejector. I would say the slide isn't going quite far enough to the rear to give the brass a good "rap" on the ejector, or isn't doing so with enough force to kick the brass out at the right time. You seem to be almost at the point of having a malfunction, so I would personally want to do something to get it to cycle correctly. If it locks back on the last round I would change the extractor if you still want to use the shock buff. One last thought--take out the shock buff and see if that cures it. If not, be sure your spring weights aren't heavier than standard.