Mystery Sound..HELP!
 

VIDEO ATTACHED. I need help trying to figuring out this loud moaning sound coming from my rear wheels typically when I am reversing and turning my wheels and slowly pressing on my break. It is a 2013 Mazda 3 4DR sedan

This started when it would rain, and every time I reversed into a stall and turn my wheels as I slowly step on the break it would make this loud moaning sound. I got my front/rear brake pads and rotors done and replaced (I believe they are after market but I will have to confirm) and for a couple days the noise stopped. It then came back and seemed to be worse and would make the noise when I again..turned my wheels to go back into a stall and slowly pressed on the break as I backed in, even when I would straighten out. It also started to make the noise if I was in bumper to bumper traffic slowly inching forward and pressing on my breaks it would make the sound. I took it to a Mazda dealership and they said that all I needed to do was lube the break pads better..so they did that and a couple days went by with nothing and then it came back. I took it back to the dealership and the shop foreman said he thinks its because there is no groove in the rotor so the vibration doesn't make a noise and all he has to do is take it off and carve that groove into them and it works every time. SOO we did that and still makes the noise.

I'm at a loss here, I have no idea what next to do..I'm thinking actually buying oem brake rotors and seeing if that does the trick but at the same time I'm scared of buying them and then it not working again. Anyone else having this problem? PLEASE HELP!