Now you add the ground lights to the mix with
the ditch lights and head lights. It sounds like
there could be pinched wires shorting together
when the shell was put on or the Legacy system is
sending the wrong commands to the engine.
When Lionel started shipping Legacy with V1.4, I had
problems turning the Cab 2 on and off and other problems
with strange engine results when pressing the touch pad
buttons.
Do you have another engine to try or another Legacy systen
to run your engine under?