OffsetSurface not working in RhinoPython script

Hello, I would like to select a surface, then to do an offset on it.
I follow the example in here but it won’t work.

import rhinoscriptsyntax as rs

surface = rs.GetObject("Select a surface", rs.filter.surface)

if rs.IsSurface(surface):
    print rs.IsSurface(surface)
    # Only with distance
    rs.OffsetSurface(surface, 10.0 )
    # With all parameters
    rs.OffsetSurface(surface_id=surface, distance=10.0, tolerance=0.001, both_sides=True, create_solid=True)
    print rs.OffsetSurface(surface,10.0)

My output is the following :


Which mean that I have the right surface (an Open Surface), but the OffsetSurface is in error. But I didn’t know why.
Did you have some advice to solve this problem ?

Thank you in advance.

Will the surface in question offset “manually” with the Offset command and the same offset value? --Mitch

Actually, if I do the offset manually, I have these different arguments :

But for the same distance (distance = 10), it works manually.

Can you post the surface? --Mitch

Unfortunately, I can’t post my work online.
But the object I’m working on is an open surface.

Unfortunately, without the surface, impossible to know what’s really happening. Does the same thing happen with other surfaces, or with different offset values?