Could you please add a check to see if inSpline is fully initialized?
If not, simply use the default Start()-mechanism to wait for it's initialization (a.k.a. while (!spline.IsInitialized) yield return 0; ). If it's initialized, further investigation is needed.
Code:
Debug.Log(inSpline.IsInitialized);
If not, simply use the default Start()-mechanism to wait for it's initialization (a.k.a. while (!spline.IsInitialized) yield return 0; ). If it's initialized, further investigation is needed.