Answer:
The direction change results from the 0% line compensation in the "Different Compensation by Line" tab for the boundary line in the support area.
This setting requires that the boundary line in the support area keeps the line length, regardless of the compensation set in plane. Since the weld lines adjacent to the neighboring cutting patterns may well change their lengths due to the compensation set for the area, the algorithm seeks a solution that is geometrically unattractive but energetically balanced.
You can avoid the abrupt change if the relevant boundary lines are allowed to relax freely in the flattening process.
