Hi, I have a Parkette Zephyr and I have taken it apart to replace the perished ink sac. The problem I have is that the cap no longer screws back onto the barrel with the section in place. If I remove the barrel and just screw it into the cap, it screws on tightly. If I add the section / nib back into the barrel, the cap threads only just meet the barrel threads and with the slightest of pressure will jump off the threads. It's something close to 1/8th of a turn and then then it jumps. The section is pushed as far in as it will go so that the barrel sits against the section and there is no gap between the two. There is a tube like unit inside the cap that creates a 'step' and this stops the section from going any further into the cap. I am not sure what it was like before I started the ink sac replacement, but I do not recall the cap coming off so easily. Any ideas of what I may have done or how I can fix it? Thank you for your help, ice70