Audi A4 B5 1999: Rear Brake Piston Issues after Caliper Regeneration & Handbrake Disc Repair

Hello!
Audi a4 b5 1999, handbrake disc.
I have such a problem that I have recently regenerated the rear calipers (seal and piston cover) and now they do not want to bounce back the pistons. In general, all the liquid spilled to zero after unscrewing the clamps. I have assembled everything, the terminals have been bled (there are no bubbles) twice with my brother on the engine off and they do not move backwards, the front ones are OK.
As I normally get into the car, the brake pedal is hard, it is hard to drive it in, after turning the engine on, you can press the pedal halfway down without using force, while the car does not brake, only from this half there is resistance and the car brakes.

What could it be ?

Air in the system

Well, I flew all the wheels twice with my brother and zero bubbles: / Tomorrow maybe we will try to pain.
Or could it be the fault of an air-pumped ABS pump?

One person writes:

The system is air in. The system also includes an abs pump

OK, I understand and I have one more question:
How do the pistons retract after braking? There are no springs on the clamps. I thought that when we release the brake pedal, the fluid goes back and a vacuum is created, which draws the pistons back, but rather the vacuum will draw fresh fluid from the reservoir.

misterbociek wrote:

How do the pistons retract after braking?

Most likely in this model, the piston seal retracts it because it brakes slightly when braking. This undo is minimal.

Bleed by squeezing the fluid out.

You did the regeneration of the clamps yourself. Well cleaned? Bleed on the fired car.

Ireneo wrote:

You did the regeneration of the clamps yourself. Well cleaned? Bleed on the fired car.

I regenerated the clamp myself, go unnecessarily, because someone was already there, because the piston is in perfect condition. Generally, earlier (blocked clamp) guilty guilt was because there was a terrible crap that I broke old blocks with a hammer.

The question is whether well done regeneration. Well cleaned pistons, piston grease used?
Because often this is a problem.

Look at the gums and you can see why they are going backwards