Hi.

I redid the basic setup I used, and was able to reproduce the error.
I basically made 4 profiles and swept those along two rails. (See attached file)

Now I've tried using several methods to avoid the bug (Exact/Auto/Refit...) but they all produce some level of bugginess. I thought I had it sorted after trying Network instead of Sweep and it looked like a much cleaner mesh with show points, but still it produced errors on Shell.