Missing lines in obj export to Fusion 360

I generated a topographical map in cadmapper. In Skethup I added volume to the terrain and exported as an OBJ. When I open the OBJ in Fusion 360 the terrain and buildings appear correctly but all the walking paths and roads are missing. The paths and roads are visible in Sketchup but not when exported. I was successful with the same procedure when using a smaller file of the same location so I am not sure if it is a file size issue with Sketchup. The skp file is only 8MB. Has anyone had a similar experience and have you figured out a fix. I appreciate the input. I am trying to create a file I can CNC. I attached screenshots of Sketchup and the OBJ in Fusion 360.