My wife has a 2012 X5 and we had similar issues. Long story short...it turned out to be the passenger side rear seat wasn't latched all the way down. We've has full size people who sat there and never even noticed or felt the seat being unlatched down all the way. We simply pushed it back with some force and clicked in. ......and yes the little clicks I was hearing eveytime I drove over a uneven surface was insane. GL with you issue.