Problem following a path

I am trying to make my characters follow a path on an oval, race track like, model. It seems as though any time the Path Marker lies directly on the incline, the characters miss it and have to turn around and go back multiple times before they move on to the next one. As you probably understand this makes for less than perfect gameplay. No amount of speed seems to solve the problem and predominately makes it worse as the characters "orbit" a PathMarker for even longer. I know some of you guys already made racing games so i was wondering whether you encountered this problem and how you got around it and also how did you deal with passing on the track. Did you create extra paths higher and lower and just attached npcs to the free ones?

Thanks in advance