Another possibility, since this came up post the direct mill mod, is there was something about the installation that is causing an issue. Have you checked the length of the screws, and in particular the screw on the right side? I have seen a slightly long screw contact the bearing thingee, which in turn interferes with the extractor working properly, and causes stoppages.
Depending upon how detailed you want to get, you could troubleshoot by seeing what happens without the optic, or try to mark the right screw snd see if it puts a mark on the bearing rod.