Two observations from me:
Where is your adjustment spur? If you have the Start and Finish at the same point, unless you measure the course once, then go to an area where you can measure different radii of turns, you likely won't hit the correct length. I normally have a spot that is used for a turnaround, so I can adjust the length of the spur accordingly.
Second, at 1st and Oak, I would come off the corner and go directly to the painted edge of the parking spot to the west (assuming a counter-clockwise route), instead of rounding the corner and making the turn at some non-defined point on the road. All turns/curves should be bound by physical objects or painted stripes that will likely always be repainted at the same spot.
Good luck!