I bought this two weeks ago. I carefully set up the tracks and placed the engine on the tracks. The engine ran after several failed attempts. I lifted the engine and tried placing it again and now it wont run...again it ran after several attempts...this happened a few times. What is the easiest foolproof way to ensure the engine runs on my first attempt of placing it on tracks?

P.S. I have watched all videos, read the manual carefully and I am sure the tracks are assembled perfectly.