I recently sent my 12 year old Christmas big hauler back to Bachman for repair. Much to my surprise they sent me a new locomotive. I was thrilled at first but the new engine constantly derails. The front carriage seems to have so much play in it compared to the original engines design.  The front wheels stay on track while the front stationary wheel comes off the track. Not sure what to do here .  The track is attached to a shelf that goes around the perimeter of my living room. The level is off a bit so am going to try and adjust that. Any other ideas would be appreciated. I admit I've never done much to this setup in the last 12 years but clean it and it ran perfectly.