FWIW, I'm a "graduate" of a Richard Binder course on adjusting nibs and have a fair amount of experience, but I'm by no means an expert. I've come across a problem that I can't figure out. Hoping someone can give me some suggestions and ideas as to why this may have happened.
The pen in question is a Montblanc 344G (gold nib). A recent eBay purchase, it writes well but catches on upstrokes, especially diagonals to the right.
A look under the microscope reveals why (see pics).
The strange thing is that the tines are flat and even and do not show any sign of prior deformation (or repair). The nib looks quite intact, in fact. Yet at the tips the tines appear to be of different lengths.
The worn writing surface is fairly obvious at this magnification and is not continuous from the left to the right tine.