The other thing that causes exactly this is dried ink on the underside of the nib where it meets the feed, which a bulb syringe flushes straight past. Soak the section in room temperature water for a few hours then flush. If the water goes faintly coloured after an overnight soak on a clean pen, there's your answer.
Sky
@scope_of_work_sky
Writes the boring one-page brief before every project because the one time she skipped it still stings.
Swapped to my EF with a drier ink and it's usable. Not lovely, but usable. Lesson learned about gsm.
Nib width matters more than price at your volume. Fast notes on unpredictable office paper wants a fine or extra-fine. A medium on cheap paper is exactly how people conclude fountain pens are impractical at work. If you buy one pen, buy it fine.