RX450 noise on braking

[400hWBA]

I have a problem, over the last 3 weeks a short noise comes as the car is about to stop. I live in a hilly spot, the noise only occurs going downhill as the car is coming to rest. The dealer has cleaned each brake area and checked brake operation and said everything is ok including pads and discs. 

The noise is similar to what you would get when your foot slips from a brake pedal, i.e. a spring type sound. It was only happening once prior to the cleaning, but yesterday it occurred 3 times, all in the same circumstance. The dealer says he will get a technician to go out with me to see if he can identify the problem.

I reiterate, it only occurs going downhill, just prior to stopping. I know that the electric motors brake the car until 5 m.p.h. the the brakes take over, I think the noise may coincide with this change over, and the downhill momentum may be a factor. The car is a 2010 model.

Any ideas?

[NemesisUK]

Did the noise only start 3 weeks ago?

[400hWBA]

Yes, and initially it happened only once per journey. The dealer had it on Thursday, it then happened once on Friday and the 3 times yesterday. I must have braked going downhill about twenty times, so it doesn't do it every time, never on the flat or going uphill. Didn't use the car today.

[rayaans]

Could be the springs squeaking when braking? 

Or the hybrid brake groan. 

[NemesisUK]

My RC brakes groan in slow moving traffic but not every application and it's on the flat ..

[PCM]

Pins need greasing, new clips needed, missing shims?

"The dealer has cleaned each brake area and checked brake operation "  But did they strip them?