Xsara Door Lock Failure

Sounds like a broken wire in the wiring harness where it enters the door. Check the rubber boot between the door and the frame for cracked or broken wires. Had a similar problem on my old Peugeot. Is the car alarm acting up too?

Thanks for the tip! I'll check the wiring harness. Is it usually an obvious break, or should I be looking for something more subtle? And yeah, the car alarm does go off randomly sometimes.

Could be a complete break, or just the insulation is damaged and the wires are shorting. If the alarm is also going off, it's almost certainly a wiring issue. Might be best to get it checked out by a workshop.

Took it to the workshop, and you were spot on. It was a defective cable/plug connection like you suggested. Cost 95€ to fix. Thanks for your help!