can't really see clearly for the grease, but what happens very commonly, is folks get sloppy about following the "H" and at certain points the pawl can get jammed, try concentrating on following the exact H that the box requires and see if jamming goes away
the box doesn't 'wear out', it gets gummed up, the spring breaks, the forks sometimes may get worn down by sloppy shifting, but that can be fixed with some weld - there should be no way the pawl can 'jump out' of a selected position,
the thickness of it is greater than the space between the forks
Bill
