Fusion’s Loft requires extremely tidy Geometry, check with Curvature Combs.
My guess is that there are either -
way too many spline points in Profiles and Rails, or
the profile spline segments have not got close to equal numbers of spline points,
(Hint: Adjust Tangent handles.
Those profiles can usually be 3 point fit point Splines, with horizontal tangent handles top and bottom, (required later for mirror seam)
adjust each handle to fit the canvass), or
more likely the Loft will build with a changed order of Rail selection, either clockwise or anticlockwise Select the rails, try clockwise.
there may may be other obscure reasons not mentioned, but there will be a reason,
@jhackney1972 , your suggestion, extended rails, - I use them for Debugging Lofts, so until we see the file, that one seems unlikely. (2 profiles, all rails, add next profile, until it breaks)
edit: I have just watched the video again, select the third rail, it should fix its own error.
Might help....
Fusion
