I finally pulled my 15-20 year old Doodlebug out of it's box and put in a DCC decoder. Then I programmed the decoder and put it on my main line. I started it down the line and then stopped and put it in reverse. It moved a few inches and then just started making a motor sound. It won't move, but the motor is spinning. Every time I try, it does the same thing. Could this be a problem in the gears? Or is this a known issue with the single set of drive wheels?