A few years ago (2018?), we felt terrible rumbling in a mid-to-aft room on Wonder for our entire cruise. The problem at that time was so bad that people posted videos on YT of items falling off the desks and tables in staterooms. However, that was a Galveston-based itinerary, which involves two long open sea portions at full speed at the beginning and end of the cruise. We went back on Wonder a year after, sailing out of Florida, and didn't notice any rumbling.
All the ships in the fleet went into a dry dock for engine work last year in France. We hoped they would fix the rumbling issue but recent reports from Fantasy indicate that ship's problems were not solved. Maybe they solved it on Wonder ?