Groaning noise while braking

I searched but couldn't find anything exactly related,

My car has developed a strange groaning noise when coming to a complete stop.... sounds like a coil spring decompressing. The noise occurs as I slowly release pressure from the pedal once completely stopped.

There is no noise when braking firmly; therefore I assume the pads are sticking to the rotor / slowly releasing in some manner.

Suspension, bushings, etc. are all new with under 12k. Rotors/Pads have under 20k.

I recently flushed the lines/clutch with Fuchs 5.1 fluid using a pressure bleeder. I can't see how this could be related, but the timing works. No issues were present before this was done.

Any ideas?

Thanks.