что в полигоне может быть неправильного, чтобы его можно было вот так просто починить?
Some of the rules of polygon validity feel obvious, and others feel arbitrary (and in fact, are arbitrary).
• Polygon rings must close.
• Rings that define holes should be inside rings that define exterior boundaries.
• Rings may not self-intersect (they may neither touch nor cross one another).
• Rings may not touch other rings, except at a point.