When setting Shape to NGRegion, the code checks whether the previous shape instance is the same and the region marks itselfs dirty only if it's different. This is wrong as the current implementation of Region in scenegraph reuses the SVGPath instances, modifies them, and calls setShape with the same instance. This can break the dirty area management as the NGRegion is not marked as dirty in this case.
Either the check should be removed, or new method to notify NGRegion of shape modification should be introduced.