Thanks Utiler and sorry for taking so long to get back to you. However, the fix has not worked on fixing the line issue. When you saved the model after editing the material properties in SU you did not turn section cuts back on. Thus, in LO the model was no longer a section cut when updated.
I do appreciate your effort though, and would love some more help. I have created a video showing the method you described and how it didn't work. I have also found a solution. Though it's not the solution I wanted.
The problem was hidden lines. For some reason if a plane has a section cut through it and the plane also has a hidden line. The plane (line in section cut) will not show in LO.
This is particularly annoying as we like to use a few hidden lines when showing elevations. (So we can seperate our upper and lower floor 3D walls but have them look as 1 item in elevation.)
Please take a look at this video:
Youtube Video