Hidden lines on switched off layer showing through

[arcsurvey]

Hello again,

I have a model of a house. I have applied a section cut face between the ground and first floor so that I can take away the upstairs and look at the ground floor with a neat cap covering the wall thickness and hiding the geometry within the wall. The visible edges on the external face of the wall are hidden so it does not show on elevation. The edges of the cap are visible so that there is some edge definition when viewing the model. The cap is on its own layer which is switched off on elevations so that the edges cannot be seen.

In layout it appears that some, maybe the inner (300mm deep into the wall) edges of the section cut face are showing up. This only happens in hybrid and Vector mode. In raster mode the model displays as intended. If I click into the model in Layout, the lines disappear.

Any ideas why this would be?

Thanks

Richard.