There are a few things that could cause this kind of issue, but Alias sometimes doesn't like having curvature leading into a boundary like was this has on the top, (and it appears on maybe on the bottom as well). Alias may be bugging out with the quick hook of the COS at the bottom over a rounded surface. You could try duplicating the top horizontal edge, and extending the top surface slightly, and then reproject that top curve to create the sliver point at the top left. Try the same extension/re-projection on the bottom if those are also curvature to that edge. I don't know why - but sometimes Alias likes that better. If that doesn't help it, I would duplicate the curves on surface, and make sure all of those are clean, without doubled up cv's, (check in your parameterization - if the spans are higher than expected, that could be a problem.) Rebuild the curves if so, and re-project. Also, remove any unnecessary curves on surface as well, like the centerline of your cutline. If it still is bugging out, a work around for your visualization could be to break up the surface so you have a smaller surface along the bottom where it wraps, (with either a trim convert or a detach) and project onto those. Hopefully you don't need to do that, but if you need to get a good visualization, that would certainly help - just keep your original for editing. I see this original post was from 5 years ago, but this can still be something I see, so just saying what I might do!
