the bulk ring is worn and the little teeth on it have started to round.
ormaybe it just needs some adjusting but i reckon its the ring.
the selector it self will be fine as thats steel but the bulk ring is brass, well a mix but were call it brass.
also, get your self another screw/bolt that holds the 5th gear selector arm part number 6100288, your prob fock the torx head getting it undone, thats the normal thing anyway.
but as above, you can do it with the box in the car, just catch all the oil that drains, it sticks, its nasty and it fucking rank shit gearbox oil so dont get it on ya clothes,if ya do, bin them