Slightly puzzled by whats happening....
For CADSTAR you are only allowed 1 board outline.
As Marce says - it is best that the board outline has its own line width assignment (so it is not affected by anything else).
When importing - the first page of the mapping file deals with the board, however in the DXF there are some rules to follow.
I.E. no splines, no blocks, the board outline must be on its own layer with nothing else on that layer, the outline must be a single continuous polyline, any cutouts in the board outline in the dxf must be on their own layer (all cutouts on one layer) with nothing else on that layer.
You need to know the names of the layers that the outline and cutouts are on in the dxf, also the units used when creating it - if it is set as unitless then set it as millimetres so the mapping file can match. It is also best of no part of the board oultine is in negative coordinates.
The copper outlines you now have in your design can be deleted.
When importing DXF's it can also help to create some extra layers to import items onto.
If your board outline in the dxf is not a single line, it can be imported as a figure onto a documentation layer instead. Then you can draw a new
board outline using the figure as a reference, using the snap features etc.
---------- Post added at 22:30 ---------- Previous post was at 21:02 ----------
Having looked at the DXF in question, this is indeed in Millimetres, the outline is OK and on its own layer (0).
This imported in easily using the default import options and un selecting the import of components.
The board outline has been changed to use an assignment of Board Outline and sent back to the OP as a PCB with the mapping file.
Although it has no holes or cutouts in.
A bit of a complicated outline, which is why dxf import is so very useful in CADSTAR, took me 60 seconds to import, would take a heck of a lot longer to draw.