If you need complex splines in Unreal then the best way to generate them would be to use your 3D package. This plugin will allow you to export data from DCC application (Blender) and then import that data in to Unreal.

If the spline loops upside-down interpolating along it can cause objects to flip instead of following the spline because Unreal uses an up vector per spline knot. When importing spline data you can choose from three methods. This can help control how the spline is interpolated and make it much more predictable.

Choose from :

• Fixed up vector
• Frenet-Serret
• Rotation minimising

Comes with Blueprint nodes that help build spline components. Also comes wit ha node to interpolate the spline data directly, without using a spline component, which is good for simply constraining an actor to the spline. Also comes with nodes to fetch knot data from the spline (counts, location, in/out vectors, up vectors etc.)