A833 gearbox 4th gear doesn't work

The only time I have ever seen the detents (pins) pop out so far they locked the slider ring was because the slider ring traveled too deep into the gear teeth and allowed it.
I have also seen the detents (pins) have the exposed end pop up and out of their slot and do the same thing.

Obviously someone modified that trans, and the only reason I can think of that the interlock teeth would be cut out like that is they thought for some reason it would shift easier (I don't see how it would because of that though)

You may find other areas where this thing was cut or ground on in the shift linkage or forks.

Looks like someone was experimenting to me.