There is a peculiarity that I did not mention, in addition to the dumbbell shape with vertical symmetry: these are two identical mirrored spirals, which develop with irregular steps. So for now, and before I look into the problem, I decided to correct the spirals with "Rebuild", Refit with a tolerance of 0.01. the difference with the original is minimal! So I no longer have sharp angles.

This subject is related to this one:
http://moi3d.com/forum/index.php?webtag=MOI&msg=10536.1

Good, have a good Christmas holiday, see you later!

- Zooen