Duck Doo -
The gears are going to look "normal" to your eye. After all, we're talking about 35 years of very slow polishing. The only way to tell if the gears need to be replaced is to compare them side-by-side against new ones from a dealer. You'll easily see then that the dogs are shorter and have a generous radius that the new gears don't have. Both the gears in the mating pair need to be renewed. Not the ratio pair, but the engagement pairing.
As John hinted, the gear misbehavior could only be a symptom. Plan on replacing all 5 coil springs in the gearbox as the cheapest insurance you'll ever buy.
:bigt
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