I recently moved my layout and now I am having problems with a couple of my cars uncoupling themselves. Before I moved it, everthing worked flawlessly. I do have 4% grades and 11" radius track on incline/declines. I know it is tight, but I have very limited space, and in all my testing it worked. The uncoupling always happens at the same spots and with the same cars. Does this sound like a track problem, car problem or both. If I end up replacing the couplers (truck mounted), is there ones that work better on steep hills and sharp corners?