Tiny thin slices of material are worn off on feed and section....the more one pulls the nib and feed, the more material can be worn off, making for a lesser fit.....
Warranty....is why one has a working second pen.....
Well you have learned a lot.
First thing you learned and quite late, use your warranty first.
You now know how to fiddle 'that' problem with a pen out of warranty.
A pen should be taken apart as little as possible....so look up the problem in the Repair Section first, and in detail before starting.
For C/C pens you now have enough knowledge .