The only problem I've found is that if the trailer you are towing has brakes, they will lock up at the slightest touch of the brakes. Also, in trying to install a brake controller to solve the problem, the installation is not straightforward. I cannot figure it out. The X5 brake controller instructions posted on the x5 forum just do not work. Close, but the x5 wiring is just a bit too different. Anyone else had this experience?