Spline Behaviour

Hey guys,
I’m working on a spline-based Rollercoaster Track right now and I got an issue with the curving behaviour of the tool.
When curving the track, I cannot control the “behaviour” of the curve itself through rotation of the adjacent points. The track in between behaves like a ribbon (the outer part of the curve contracts and the inner part bends), but i want it to be the exact opposite way (like a tube). Please check the pictures for clarification.

Now, the thing is - this does not happen with EVERY curve, just sometimes in between the track, between two random points. Sometimes this doesn’t even appearfor the whole length of the track between to points, but the track just seems to change behaviour randomly in-between from ribbon to tube.
Any thoughts on this? What could be the issue here? Do you think this is even caused by the spline-tool, or by the track-generation written on top of it?

thanks in advance for your input,