UNWarp U misjudges corner angles.There are differences among the three plugins. Hope ZenUV can improve this aspect.
This operator works correctly if you leave the outer boundary edges of the island unselected; in most cases, this is sufficient. I’ll add this specific scenario to our Feature Request list. However, I need the island mesh to understand exactly where the issue lies. Could you please send the geometry that causes this behavior?
test1.blend (112.5 KB)You can try to straighten that curved line as shown in the video, then relax it along one direction.