The right rear brake makes clicking noise when engaged. Repaired three times.

Rear brakes on this vehicle are old style conventional drum brakes - with shoes that push out from the actuation of hydraulic wheel cylinders to contact brake drums. The contact causes the vehicle to slow as a result. If there is clicking noise, it could be brake hardware -- springs and cables that are attached inside the rear drums, or it could be a contact issue with the drums themselves. Sounds like the dealership has identified the drums as a concern -- ask why they want to solely replace the drums; it's not making much sense without further information.