What did the shifting fork peg and the camplate groove look like after 33 years of the peg moving the camplate?
When a gearbox is jumping out of gear I always ask myself whether I'm sure the box ever gets fully into the gear that's jumping out.
I'm posting two images to help visualize the problem:
The shifting mechanism:
The position of the camplate and the inner quadrant when the gearbox is in 4th gear: