Back in the day of MX, before corridor modelling, when an earthworks slope was cut and it flipped from cut to fill the earthworks would reduce in size to the point at which it flipped i.e. the line touched the reference line, and then go back out again…

I'm using the create cut fill volume tool which picks up the whole design model against the existing terrain except one triangular looking area: I even tried swapping out some of the corridors: Any ideas what type of situations cause this? It…