Handbrake control light during braking and in curves at the SX4 classic,

Today our son visited us with wife and the two grandchildren. He drives an SX4 classic, year 2012, 120 hp gasoline, 4 disc brakes. He reported that when braking and in bends the hand brake control lights light up. I did a test drive directly and found the same. A check of the brake fluid level showed that there was a lot missing. The car has 112,000 km on the clock. My suspicion is that the brake pads are front or back and thus the fluid level is The fatale: The daughter-in-law was in front of the car last week because of exactly the thing at a free workshop. The diagnosis was: they can continue driving, that can only be a sensor. The same workshop had changed the front cathedral warehouses at the car in the summer. So they must have dismantled the brake calipers and seen the brake pads. Such a workshop would have to be sued or ?????? I’m going to take his SX4 to the Suzuki dealer of my trust tomorrow. What do you think about this?