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Twice now, the modern Sheaffer cartridge in this pen has slipped off the nipple into the barrel, discovered after some ink appeared around the section joint. The pen has just been lying flat on my desk since my previous post, not dropped or carried, and I have no clue why the cart is coming loose. I found a spring just slightly smaller than the OD of the cart and about 1/4 inch long and dropped it into the barrel to "encourage" the cart to stay in place. We'll see what happens.

On the plus side, the ink has finally displaced the remaining water from the tip, and it now writes a nice black instead of a watery grey.