I have been working on my couplers over the past few days and the only issue I seem to constantly have is when it comes to uncoupling... the whole process is fine except that it seems the couplers don't open enough and as soon as they move away from the magnet, they snap back and the cars are again coupled. The couplers are Kadee's for the most part, and gauge is correct, as well as height... maybe new magnets? Help please!