Offset Curve Component weird behavior

A weird issue with offset curve component when i try to offset a closed irregular polygon curve the curve and X amount get broke and appears just a part of my original curve. 

but if i do it manually in Rhino the offset its well done. 

anyone can explain me whats happend ? 

In the image above i do a manual offset of 6 units in and out of the magenta line. 

In this i try to replicate the same operation with GH but at the amount of 6 units something weird happend.