I would guess that the alcohol is good at removing grime. I would guess that an eraser is better at cleaning the wheels for electrical conductivity. I would lay the engine on it's side and try applying power to the wheels.
If you could borrow or buy the roller stands made for cleaning, it might be easier. Maybe there's a broken lead to one of the trucks making this engine more sensitive to the track?
I would pull the shell and test directly if there's no warranty .
Again I don't do much with HO stuff anymore and I'm way behind what's going on there. I'm forced to maintain my G and O scale engines regularly and I feel that the issues must be similar? The old Athearn blue box engines I had ran fairly well. I remember adjusting a metal tab that rubbed another above each truck for power pick-up. Other than that, I really don't know what's inside a current model!
