Please try disabling Hardware Acceleration by starting Freestyle with /nohardware switch:
1. Right-click the freestyle icon on your desktop > Properties
2. By default the Target is: "C:\Program Files\Autodesk\AutoCAD Freestyle\acadfs.exe"
3. Add a space and then /nohardware at the end, so the new Target would be:
"C:\Program Files\Autodesk\AutoCAD Freestyle\acadfs.exe" /nohardware
4. Apply > OK > Re-launch Freestyle
Regards,