We were in a rear facing balcony cabin on Fantasy two years ago on deck 8. When we were underway that ship had the slightest little 'wiggle', probably from wave action against the back of the hull. HOWEVER, after we left San Juan, they were running fast to make our stop at Castaway Cay and we had a very well defined vibration appear. It only was apparent when they threw the throttle open and ran fast. We were starboard of the center line, and we didn't get any banging or clanging like is described other places on this post, but we did have some 'symptoms' of something out of balance, like a prop or prop shaft...
We have a similar cabin on deck 9 for a cruise in Feb of next year. It would be nice if this vibration was gone after the dry dock stay...
Tom in Okeechobee, FL