Sorry for my English....
Custom mesh in Dragon Bones erases 1px (right and bottom). The picture is distorted.
0) Lets create circle in Adobe Illustrator.
1) Export it to png (with transparent). Look at the circle. It fits exactly into the picture. There are no extra pixels around the edges. Picture end-to-end.
2) Import circle to Dragon Bones.
3) Create a custom mesh.
4) Custom mesh "erase" 1px right and 1px bottom of the image.
So we can not Export grafics from Adobe Illustrator without editing. We must open png image in graphics editor and add some (1px or more) "empty pixels". Because one image pixel right and bottom will always be erased when we start edit a mesh.