When exporting flat patterns via Export Flat Pattern module, output DWG/DXF files include the sketch segments from the sheet format
CAD+ Toolset is using default drawing template to produce DXF/DWG file. Sheet format will be removed form the file, however if template contains the sketch segments on the sheet (not sheet format) those will be included in the output
Issue can be fixed by changing the default drawing template in SOLIDWORKS.
Alternatively, create an empty drawing template (without sketch segments and sheet format) and save to %localappdata%\Xarial\CADPlusToolset\Modules\flat-pattern-default-template.drwdot. CAD+ Toolset will check if this file exists, and use it instead of the default template