Does anyone have any ideas, very frustrating, everything was working fine, I left room came back engine dead, I know track has power, light on other rail car work fine?

Engine just stopped, there is power on track, engine is just dead (second time) first returned to Hobby Lobby?  Is there any Warranty?

I tried a second controller and that worked then swapped back to original controller and that worked.?  Unrelated follow up question, what is tnn repurpose of the Rapio couplers included in each set,

This is my second set, the Sky Chief N-Scale Engine seems to be frozen, the light come on and I can feel vibration but train does not move, any recommendtions?

Thanks