Hi there. Sorry for late response.
I have created a new Open World Level, placed the BP_SnappyRoads into the level, created a Layer named “Roads” and set it to Reserve for Splines.
I then created another layer and put the Roads Layer to the top of the stack.
Then i pressed Deform Landscape, which worked out just fine.
But when i then move one of the spline points the engine crashes and i got the error mentioned before.