problem with MTH caboose hitting center rail

I have an lionel O27 manual switch i bought a new MTH caboose when i go into my siding the bottom of the outside truck frame hits center rail to the main track shorts out and when im running on the main the outside truck frame hits the center rail going into the switch i had two cabooses does this in MTH my other mth don't do it have any of you have this problem what you did to fix this problem any you guys input be greatly apperciated Thanks Jeff