My French Windows have security bolts fitted to the top and bottom edge of each door. These locks are closed or opened by rotating a brass knob fixed to the escutcheon plate. When unscrewed these plates have a splined rod extending from them. These are quite ordinary and commonplace bolts.
Unfortunately the female inner part of the lock is obviously worn since rotating the knob fails to have any effect. The splined rod shows no wear. Since the door cannot open, one is denied access to its top edge. How can I fix this when I can't get access ?