Just to be pessimistic, John, did you check the state of the cable in the 'banana-shaped coffin'? That cable transfers the rotation of the door key to the 'dog bone'. If it has failed, due - I judge - to fatigue, it will need replacing. There is a detailed How To here:
https://the75andztclub.co.uk/forum/s...d.php?t=303470
Derek.