Seat Ibiza Brake Pedal Vibration

That certainly sounds concerning. I experienced a similar issue with my older Volvo, though the symptoms presented slightly differently. The pedal feel was inconsistent. It turned out to be a combination of worn brake calipers and old brake fluid which caused undervoltage and reduced brake performance. Have you checked the condition of your brake fluid and calipers? Is there any corrosion visible?

That's interesting about the undervoltage. I hadn't considered that. How exactly does old brake fluid contribute to undervoltage? I thought it was just about braking performance.

Indeed, old brake fluid can become contaminated with moisture, reducing its effectiveness and potentially causing corrosion within the brake system. This corrosion can increase resistance in the electrical components of the braking system, such as the ABS module, leading to undervoltage issues. Given your symptoms and mileage, a thorough inspection of the entire braking system, including the brake rotors, brake shoes, and brake fluid, by a qualified technician is highly recommended.

I took the Ibiza to a trusted mechanic, and you were spot on! It was indeed a brake issue made worse by undervoltage. They replaced the metal brakes, brake shoes and brake rotors. The total came to 240€, a bit more than I hoped, but at least it's sorted. Thanks a lot for your help!