Handbrake problems

Hi, was this weekend in the workshop to have my brakes renewed. I also had the car checked out. At the check you have (allegedly – I didn’t notice anything about this before) then noticed that the hand brake does not work synchronously. Despite an exchange of the disc and the block only the hand brake is asynchronous and the normal brake does not work. I have to say that my V40 2.0 has four discs and thus also brakes at the rear. The rear brake does not work perfectly only the hand brake. Now the workshop has informed me that the brake cylinders have to leave the back. Is that right? I don’t understand that he brakes correctly with the foot brake and the hand brake does not. Can anyone help me here? Greeting Ma28