It has had the upgrade kit... years ago!
UpsShifts are positive and firm, never slips out of gear.
Now that I think about it, As it happens more, when I downshift sometimes I can feel the shift lever not bouncing back, just a click not a positive CLUNK. sometimes it takes a few seconds to bounce back.
When it gets "stuck" the shift lever feels like it did not return to a shiftable position.
I was thinking the Gear change return spring.
I see of the schematics that it can come as a whole assembly (Gear change Shaft Assembly) I wonder.. Can I change this only with the front cover off or do I need to take the bottom off too?