the line thickness when importing DXF is wrong.
The exported files become corrupt lost thickness information.
Open a DXF file with line thinckness set, use the attached as test.
The line property "polyline width" is not rendered
Export as DXF
Open the exported DXF with QCAD pro, the line thinkness is wrong
the problem is present in LibreCAD and QCAD Community edition too, see:
QCAD Pro and Autodesk TrueView open DXF correctly