Lofted plate issue - not behaving as within TEKLA

Not in the official link I’m afraid.

In general lofted plates are a bit delicate in Tekla - this is a core bug/limitation. I.e. even if you manage to pick those exact points in the Tekla UI, you would still get an invalid plate. Sometimes shifting the control points just a fraction of a mm in any direction might bring the plate back.

You are often able to get working input curves by Rebuilding the input curves, or Divide them into segments and re-join the points as polylines, or a combination of the two. But finding curve degrees and division counts that work for all plates is tricky.