I have three On30 trolleys in my Christmas village. When I set up this year, one worked perfectly, and the other two won't reverse. Because I have three sets, I have checked every connection, switched trolley barns, switched final reversing track, and switched trolleys -- none of these troubleshooting ideas has caused the the trolley to reverse. It goes to the end of the track, stops, and stays there. Please help me troubleshoot how to fix this. Do I need a new barn, a new trolley, or a new final reversing track (A to "connect to bumper")?  It is a fairly long run of track, but the trolley runs fine until it gets to the end and doesn't reverse. Greg