XC40 brake booster pressure sensor failure

I had something similar with my XC40. A pressure sensor issue also caused braking problems. Have you checked the brake pedal?

What exactly did you find wrong with the brake pedal? And how did you resolve the poor braking?

I didn't check the brake pedal, a workshop did it for me. From what you've described, I think it's best if you take it to a professional workshop for diagnosis. These systems are complex, and messing with the brake system or ABS system can be very risky.

Took it to the shop, and you were spot on! They confirmed it was the brake booster pressure sensor. Apparently, someone bungled the brake bleeding previously, causing the sensor to fail. 90€ later, all sorted!