Fixing CSG error locations

I have had an issue when building a faulted geological model using borehole data. When I developed the initial unfaulted mode, there was no issue at all and it processed fine, however when I use the same data to create a faulted model, several fault blocks do not process correctly, with units sitting side by side instead of on top of one another. This is despite having "snap to data" switched on. I have received an error saying that the meshes are not closed, and data added into the "Points" folder showing "Surface Chronology CSG Error Locations" which I can view, but not do anything with. Is there a simple fix for this?