On/Off Brakes!

[luminmiller]

I am having a very puzzling problem with my brakes:

All 4 wheels spin freely when jacked up, but when the car is turned on and the brake pedal is depressed
the brakes stay engaged slightly. If you wait a couple seconds the brakes release or if the turn the car off
the brakes release immediately.
(like a hydraulic issue not a mechanical one)

The Car is a 1996 E39 523 originally with asc (asc now deleted).
The brake pads and rotors are new.
The fluid reservoir was completely drained and has been refilled.
The ABS pump bleed procedure was done using a computer (all air is out of the system and the brake pedal has a perfect feel)
ABS light comes on and goes off with the key (as it is supposed to)
No fault codes except one that the asc has been deleted.

When I tested the wheel speed sensors on a computer only the front right showed any reading.
The other three showed no speed when I rotated the wheels.

Could wheel speed sensor failures send bad reading to the abs and cause the issue I am having?
The shop I go to wants to throw parts at the problem (new abs pump, new brake booster), but I thought I'd ask around first?

I hope this is clear and if anyone has any pointers please chime in.

I am a seasoned mechanic but this problem has me stumped.

Kind regards
Lumin

[luminmiller]

Could the brake master or booster cause this kind of problem?

Kind regards
Lumin

[luminmiller]

Found it to be that the aftermarket brake pedal bushings were to tight holding on to the pedal.
Easily solved but many hours in the discovery.