Our only experience is our pool. I don't know why you'd get this problem unless two sections of your coping meet at the same place that two pieces of your wall meet, and settling has occurred.

I wouldn't bang anything. Since the coping is attached to the walls, you could break or bend them, plus who knows what would happen to the concrete inside the coping?

Personally, unless you can find out the cause of the height different and fix the cause without doing more damage to something else, I wouldn't mess with it. Jo