Need some help! My layout has 14 turnouts with lotsa switching & coupling/uncoupling opportunities. I've installed 7 undertrack magnets which generally work well. Occasionally I'll buy a new M/T car that won't uncouple although the coupler swings when run over the magnet. It just won't let go of the mating coupler. I do all the checks & adjustments that M/T recommends & spray with Grease Em. Doesn't help. What say you experts? What am I missing here? Need to magnetically uncouple as the layout is 4'6" x 8' & some locations are hard to reach.