Its sticking on something for sure..... My guess, doubt its magnets..... Mine stuck in 8 different places , and would do the nudge thing also, look really, really close,,, sometimes the upper wheel will be catching something from the top, something there is making it stick... bet an oz on it..lol now that my track is straight and cleaned (used sandpaper) it rolls fine pulls harder when Temps are higher (rubber wheels soften a bit).. and it pulls all the cords with it, but the cords need to be strategically placed and hung just right.. get a chair or a ladder and get up there and run it back and forth on the sticky spots, you will see something.... (mite carcass&eggs, half a blunt) aluminum shaving perhaps... a lubricant will only worsen things, it will make the wheels slip,, the rubber likes to be warm for best traction, just like a car tire... tell us what you find...