Well, I've had many trips to the garage and lots of heartache over the same sort of problems...on both rears. Though, once the issues are sorted it's all plain sailing again.
These are the possibles...
1 - The handbrake works by drum-brakes which are inside the centres of the discs. These are held together with springs and cups, if they come apart then you'll get scraping and clunking noises.
2 - There is a backplate behind the disc, which can get bent towards the disc. This can scrape, causing noise, especially when turning.
3 - There is a backplate behind the disc - only visible with the disc off. This can also get bent and then rub.
I've had all of these at one time or another. Not dangerous, just :tsktsk: annoying and fiddly to find.