When you convert a DWFX back to DWG, the software is essentially performing a reverse engineering process. The DWFX file knows where a line is, but it may not know what that line represents.
When a native DWG file is plotted to DWFx, the "intelligence" is stripped. dwfx to dwg
This is the most reliable method for users within the Autodesk ecosystem, as it does not rely on intermediate interpreters. When you convert a DWFX back to DWG,
How to convert DWF files to DWG format in AutoCAD - Autodesk dwfx to dwg