I have questions like other posters... Too much oil? Why would they have to resent codes for too much oil, sounds a little questionable to me! The gear indicator could have been an electronic problem or a mechanical issue. With the noise you experienced I would guess there was a mechanical problem. As someone else mentioned I would definitely ask what codes were reset and once they tell younthat, why were they reset! How did resetting those codes stop the rattling? Luckily I have an outstanding dealer and service department that over the years have earned my trust by always being upfront with me and explaining any issue found, the cause and the resolution.
Best days to ride end in "Y"