especially with air pressure changes (e.g. air travel) LOL, yes, I've made that mistake before.

After your comment, I took the pen apart to see if I could see anything. It completely saturated the paper towel I was using to hold the nib. I think the problem started after I changed the cartridge for the first time, so maybe I damaged it doing that. I am going to put the converter in and see if that helps. Otherwise, I'll take your advice and get a new one. Or something else.