Rear Breaks

I have a 2001 Chevy Cavalier, With ABS. Starting winter my rear right tire started locking up and causing my car to bend down to the right. It doesnt do it all the time, but does do it often. It only does this when I am stopping. And once im stopped and let off the break my car pops back up from being bended down and makes a crack noise. My dad took my drum off to see what it could be and I still have a quarter worth of shoes on the back and my drum seemed fine, but my breaks were pretty spreaded out, so he fixed it so the drum went on way more easily, and that was a week ago and it hasnt done it since, except its starting to do it again. What could it be?