After having my rear brake pads replaced and rotors resurfaced, the
left rear wheel occasionally makes noises when coming to a slow speed
stop, with the brakes lightly applied.  It seems to happen more when
the car has been driven some distance.

It is a soft metallic clunking, but easily heard and felt, proportional
in frequency to the speed of the car.  The clunks happen several times
per rotation of the wheel.

Had it back to the shop twice, they took it apart and lubed but can't
find the problem ..  Of course it doesn't do it when at the shop !

Any ideas?