Twizy headlight range control fault

That sounds frustrating. I had a similar issue with my 2016 Opel Corsa. The headlight range control, sometimes called auto-leveling or adaptive headlights, is supposed to automatically adjust the light intensity based on the car's angle. Usually, this is done via a servomotor within the headlight assembly itself. Does your Twizy have adaptive headlights? If so, the servomotor could be defective. Have you checked the wiring and connectors to the headlights? Sometimes a loose connection can cause issues with the lighting system.

Yes, my Twizy has adaptive headlights. Where exactly is the servomotor located, and is it easy to access for checking the wiring?

The servomotor is integrated inside the headlight unit itself. Accessing the wiring can be a bit tricky depending on the car's design, but usually, there's an access panel in the wheel well or under the hood near the headlight. Since the problem is intermittent and affecting both lights, it is not just the connectors and I recommend taking your Renault to a qualified workshop. They have diagnostic equipment to pinpoint the exact cause. This might save you a lot of time and frustration.

I took it to the workshop, and as you suspected, the servomotor in the headlight was defective. The repair cost was 1040€.