I am building my new layout after all my rolling stock has been in storage and has suffered several hard moves. One of my pieces is a doodle bug (walthers?) is lurching when I run it. I took it apart and everything looks fine. It has a cheap digitrax decoder in it. all the parts seem to move fine. It has a rubberband drive but the rubberband seems to turn easily. The decoder plugs in to a flat conector. I am thinking about removing the decoder and put little jumpers in the harness to see if it runs smothly on DC. Any suggestions to other things to try before tracking wires to figure out where goes to what. I installed the decoder years ago and to the the best of my memory it worked when it went in to storage.