20-02-18, 06:55 PM
Hi Rikki, and welcome.
The fault may just be with the selector. If so, it is probably fixable without removing the engine as the drum and forks can be replaced from the side/underneath. The ratchet mechanism that nudges the drum round can also cause issues.
This link takes you to the problem I had and there is also a link in there to all-round spannering wizard Deefer's detailed description of the drum and forks replacement process. (Even if you don't want to tackle the job yourself it may help the mechanic you employ to do it.)