There seem to be a lot of people complaining about loose/rocking seats. All you have to do is tighten the 4 bolts that attach it to the floor. It takes
a 14mm socket wrench and 10 mins.

My bolts were loose on both driver and passenger sides next to the center console:


Pop off the cover and tighen:


Check the back also:


And done! My passenger side still rocks but this is due to the rails being loose I think. My driver side is solid.