I won’t be at a CPU until late next week, but I’ll try to remember to look this over. 9/10 times it is because your solid has a face with an inverted normal (points into the solid instead of out of). You can test this by finding a point and normal at UV parameter 0.5, 0.5; and using a Geometry.Translate By Direction Distance method to move the point by a small amount - say 1/10 of your shortest edge; then ask if the translated points intersect your original solid - if so those faces need to be reversed. If not you’re up against something else.