I bought a Bachman 2-6-6-2 locomotive at the last train show. The engine ran well but always derailed on curves. The problem was the orientation of the pin connectors. Under the cab, the loco/tender connectors faced down instead of the usual rearward mount. The wire bundles would hang on the drawbar and derail the lead truck of the tender. The easy solution was to take brass strip and make a new drawbar. The new drawbar has a depressed section to clear the wiring bundles. Now the engine is a good all around runner. Has anyone else had this problem?
Had a similar problem with a Spectrum 4-8-2, even though that drawbar had a depressed section, but I solved it by cutting off the wire wraps and pre-bending and re-routing the wiring a little. The drawbar "mechanism" on the Spectrum J didn't let the loco straighten out all the way exiting curves, and you couldn't push anything backwards, even straight thru a switch, without derailing. Replaced their "link" with a straight drawbar, and now it runs great.
