This issue occurs if there is data well outside the expected floor plan extents. To determine this, open an affected floor plan SWD in Cadcorp SIS and use Home / Zoom / Zoom Extents. Such data may be present in referenced or imported DWG files, and is often graphically invisible.
The following solutions are available:
A suitable line thickness can be obtained as the value of a CSS stroke-width in an SVG file compiled from a floor plan without the issue.
If you need further assistance, please contact IFM Support <support@integratedfm.com.au>.