on a corresponding shelf in the extractor. As Bill has suggested, the plunger may be turned or disfigured and not be resting where it is supposed to be. It is not uncommon to see it assembled incorrectly and you may need to dress the shelf and plunger with a small file to get it right. It looks like the extractor is being pushed far too much and of course will absolutely refuse to jump onto the cartridge rim if too much pressure is applied via the plunger. I'd sure take it apart and clean out the crud, that in itself may cure your issue.