Reply to "What does one do with MTH product defective still under warranty???"

With all due respect, don’t over complicate things; either the dealer fixes it or if they cannot, you get a refund.  Pay with a credit card for additional assurance if you want it - no credit card agreement will allow a merchant to unload defective merchandise on a customer and not take it back for a refund if it cannot be repaired or otherwise made right.  The only risk is that you may not be able to get a copy of the locomotive you want but typically they can be found.