Hi Fred,
Great plugin! I found an issue where when editing the points on a closed curve that defines a surface - sometimes the surface will break for no reason. It works as expected on most edits but regularly there are some edits that just won't work, even when a plane is selected. I haven't been able to establish a pattern of what causes the issue to happen. I found a workaround for the moment but it's time consuming - once the surface disappears after an edit, I copy the curve and paste onto a new surface. My workaround actually proves that my curve is still flat and the issue is indeed a bug. Please let me know if you'd like me to send a video of the reproduction.
J
EDIT:
Here is a link to the a reproduction of the issue: https://www.dropbox.com/s/k0ilok2zwdcay6n/Sketchup%20FredoSpline%20Bug%20Repro%20HB.mp4?dl=0
As you can see toward the end of the video, editing the points sometimes break for no apparent reason. This has been a workflow killer for me as it prevents from editing curved borders in situ.
PS: Unfortunately, I was not able to attach it here as mp4 are not allowed.