Rear brake brakes unevenly – tips?

Hi guys, I was with my C4 at the Tüv, and the car failed due to unequal braking power of the rear brakes. I then had the rear brake replaced by a colleague, because the brake blocks and the discs were pretty low. Again on the brake test stand, and the uneven distribution became even worse. The right brake caliper almost stopped from the number 1 (10 kilosNewton?) . The left saddle continued to pack. That was only the case with the hyd The braking force of the hand brake was even. The caliper was not fixed at the brake block. It could be screwed in just as easily as the left one. Both saddles were also made superficially clean. The things were also completely dry, so no loss of fluid. The brake fluid was changed almost 2 years ago (will definitely be changed this evening). Does one of you have a tip on what that might be? I personally did not have any I’m not really in need of the experience, like a real car mechanic, either. The colleague with whom I fix the whole thing is a car mechanic. We couldn’t quite explain it so far. Since the caliper is smooth and dry, we actually assume that the caliper is in order. Especially since the hand brake is ok, should it only be due to the hydraulics, right? I got the rear brake hoses and replace them tonight. easy one of these is defective and leaves only a certain limit of pressure to build up. It is such a guess of me. Buy and install just 2 new brake calipers for just under 300 euros is now also not necessarily my favorite hobby. Especially since the car has cost me 600 euros in the last 2 weeks. I would be pleased about every tip. Greeting Christian