Modelled this arc from 3 points in a polar array with PFrames along a curve.
It works fine at certain points along the curve but gets twisted at others.
Is there a way to avoid this?
Yes, in some situation Frames could be twisted in a unpredictable way.
You can use “Align” with a vector pointing to the center of the main arc to give the same orientation logic to all the frames.
(I did rebuild your definition…) LGK Troubleshoot_re.gh (16.6 KB)