rear brakes binding

[A8 Owner]

thats the thing it had only failed MOT on the 2 things track rod ends and airbag light. So just went in for them. As MOT tester said brakes passed last week and drove it fine on tuesday to them. He even said it drove fine into workshop. Only thing the car elec bloke did different to air bag fix was put two resister's in,as i think he said other wise seatbelt would of had to be plugged in all the time. Im just wondering if there was anything he could of done, when fixing this has caused this problem.