VelSatis radar sensor failure

That sounds similar to what I experienced with my old Volvo. I had the 'collision avoidance system failure' message. Have you checked if the radar sensor itself is clean and unobstructed? Mud, snow, or even a thick layer of dust can sometimes interfere with its operation.

Thanks! I hadn't considered that. Where exactly is the radar sensor located on the VelSatis? Is it easy to access and clean myself?

On the Volvo, it was behind the front bumper, near the fog lights. I would suggest getting it professionally checked. It could be a faulty sensor, but it's best to confirm. If it is a dirty sensor, the workshop should be able to check it for little money.

I took your advice and had the radar sensor cleaned by a mechanic. Turns out, it was just caked in dirt! Everything is working perfectly now, error messages are gone, and it cost me only 45€.