chabashvili

Hi guys,
So I imported dxf from sketchup. I have there separate group for the mesh I made there from cad file. When I import it to Houdini it has this white edge around it. And I can not get rid of it. If feels like its separate (in group selection it is separate), but no matter if I blast it or dissolve it it just ruins the mesh - it deletes edges. I've tried Fuse, Clean, PolyDoctor - nothing helps. The only solution I came up with was to inset it a bit with polyextrude and then deleted the edge. Is this a normal approach? Is there any other elegant way doing it? Am i missing something? Or this is dxf thing and there is a way to deal with it? Thank you in advance for your time. Cheers.
(screenshot attached)