Reply to "Lionel 027 Scout: Why does the flat spring on rear coupler force rear truck upwards, instead of downwards onto the track?"

Lionel changed the design of the trailing wheel and drawbar a couple of times over the years.  Can you post a pic?  Maybe a previous owner messed with yours, or you have the wrong parts for your loco.

That being said, on O27 especially the 5121 and 5122 switches, all bets are off.  Backing through the curved leg of a switch, especially when pushing a load might well result in a derailment.