cloth Surface Penetration not working

Hello, this is what I did:

1.Model a Cape in blender->export it as FBX

2.Drag & Drop FBX file into Unity scene

3.Add cloth Component to the Cape -> under 'Mesh' , the Cape Mesh was already selected ->Click on 'Edit Constraints' : set Max Distance on Top of Cape to 0, middle part 0.5 and bottom 1

4.Hit play -> cloth simulation worked

5.Click on 'Edit Constraints' again : select Surface Penetration then select all vertices and assign 0 to them

6.Hit play -> cloth goes crazy, even though it doesn't collide with another mesh !

I am desperately trying to fix this since 4 hours ! Nothing works, the cloth always goes crazy when I put Surface Penetration to 0.

Please Help Me