I'm having trouble with a factory sound-equipped Spectrum Heavy Mountain (SP with Hicken) that I recently picked up second hand. The sound is fantastic -- beautiful, deep, throaty chuffs, which continue even after the loco comes to an abrupt halt without cutting off the throttle (I use a Digitrax Zephyr). A shove gets the engine moving again, but not for long. Since the sound stays on, I can be sure it's not an electrical problem. I'm guessing there's a bind in the side rods or the gears. I'd appreciate hearing from anyone who may have experienced a similar problem and can recommend a solution. Thanks ...