Brake piston rear right firmly

Hi, everybody, we have an Audi V8 automatic quattro, Bj. 1992 In this vehicle, the brake warms up to the right rear more than to the left back. We suspect that after a long service life, the piston with the handbrake tightened (6 months) does not go back completely. The brake discs, tongs and pads were re-made two years ago. Who knows advice? LG, Christian