Maria we were just on the 9/27 sailing from Istanbul to Athens and stayed in one of the 7 sitting cabins. I didn't notice any gas smell but there were some vibrations. The vibrations were stronger when the ship was docking or making turning maneuvers. Although it occurred sometimes when we were sailing it wasn't very pronounced during those times.

I did notice mustiness on the seventh floor near where the elevator and stairs are. Our cabin was about 10 cabins aft from there and we never smelled anything in our cabin or in the hallway outside of it. And I have asthma and am very aware of strong odors as they can bother my breathing. In fact, almost as soon as you headed away from the elevator area in the aft direction it seemed that that the odor dissipated. From what I'm reading here, that may not be the case in the forward section. We also didn't have any plumbing issues in our cabin.

Another place I noticed a musty/mildewy smell was in the show lounge (Windows). On the entrance level it wasn't too noticeable (although it varied throughout the week) but if you went up to sit in the side balcony area it was VERY strong. We tried to sit in the right-hand balcony area once and immediately got up and went back down to the main seating area.

I'll add here that overall we enjoyed our first Radisson cruise and the Diamond. I do plan to post with some additional observations on the cruise and the ports once I get things at home back in order. We stayed the weekend precruise in Istanbul - which was fabulous - and enjoyed every stop on the itinerary.