Try this.
Per Lionel tech support, Switch the engine to "prog", put it on the track and apply power. Then, while the engine is in motion, Pull the plug on the transformer. After 10 seconds, Switch the prog/run switch to "run", put the engine back on the track, and slowly re-apply power.
It was recommended to have a load on the track when power is re-applied (a lighted caboose is fine.
.