Citroen C3 2005

Very low mileage (only 54,345), great running and clean car. Timing belt etc done July '26 (as it had never been done) and bonnet resprayed in early August just for cosmetics (surface scratches) and has 5 good tyres so have put a little money into it recently. Since then, the central locking has engaged and all doors stay locked. Drivers door opens from outside. Think it must be electrical issue but don't know. NCT due end Sept '26. It may be a very simple resolvable issue but it's not worth me putting more money into it. Open to reasonable offers.