I have a random rolling thunk in the rear of my car. I thought it was a loose spare Tyre. I’ve taken it in and they’ve replaced the c-clip in the brake drum, but it’s still happening. It happens when I brake, sometimes when I turn , random on a straight. And not constantly.
Likely something suspension related. Shock/strut mounts, sway bar bushings, etc.
Try a different mechanic.
Concur, suspension system seems more likely culprit than brakes. Those C-clips can be problematic tho, often reused when new ones should be installed after brake jobs. So new C-clip probably worth a try, no harm done, and you now have new C-clips.
Can’t speak to your car’s rear suspension design, but my Corolla has struts, control arms on each side, and a stabilizer bar w/links from one side to the other. On a 2010 pretty good chance something among those parts is loose. Rubber control arm bushings, strut mounts, links, etc. They all have to be checked by putting car on lift & prying on them, looking for more than normal amount of movement. Braking, turning, bumps causes movement in suspension system parts, and looseness will cause clunks and other noises. Might pay to pony up for new struts on all four corners as part of this repair; car owners often don’t notice how the ride degrades with use b/c it changes so slowly. But 4 new struts will likely return your Accent to a like-new ride feel.