Master door locking issue

That sounds frustrating. I had a similar problem with my 2018 Opel Corsa. The central locking went haywire. Have you checked the wiring harness that goes into the door? It's a common point of failure and can cause all sorts of weird electrical issues, including problems with the car alarm.

Thanks. Which area of the wiring harness should I focus on? Are there particular connectors or sections known to be problematic? I'd like to inspect them thoroughly.

On my Corsa, it was where the harness passed from the body into the door – constant opening and closing flexes the wires. I'd carefully inspect that section first, looking for any breaks or chafing. That being said, given the complexity of modern vehicle electrics, it might be worth getting it properly diagnosed at a workshop.

I appreciate the advice. After a diagnostic check, it turned out to be a faulty connection, as suspected. The repair cost was 95€. Thank you for pointing me in the right direction!