I am encountering this in a super eastern PA and NJ route that I'm working on with Reading and Northern and NS Reading Line routes merged with my own DEM. I was trying to delete a track spline point on a spur and I get locked by parent. I can delete the track, and move the track at one end, but I can't move the locked by parent spline point. I guess I could just add a spline point then delete the part of track where the locked by parent spline point is.