Did you find a solution to your issue? I’ve run into the exact same problem in my Houdini Mapbox to unreal workflow.
The splines behave normally at first but after a few days I will try to add new points or new splines and those will be behave in the above manner.
Edit: this is still an issue after reopening in 4.25, i’ll try rebuilding it using exported heightmaps and update if it becomes an issue again
