With a vintage pen, stuff can break, even when you follow your repair procedure properly. You're dealing with a vintage pen, and then your replacement parts even are often vintage as well. The materials can change shape, shrink, and degrade over the years in some cases. I just threw one pen into my donor drawer because the barrel had shrunk noticeably but the cap had not. The barrel and cap would not even come close to engaging. It was a part of an online junk store trove of pens and parts. A week earlier I'd fixed a pen from the same maker, same era, same model - everything fit together snugly and it fixed up just fine. The fixed pen probably got much better treatment over the past 83 years. Repairing vintage pens can be like getting your arrow into a moving target while shooting from a moving car.