This is an inconsistent but frequent issue. Often a solid surface will hide guide lines or make it impossible to accurately place lines and shapes on the surface because the preview guides are all hidden behind the surface. I checked to see if for some reason the surfaces don’t line up on the axis, but they seem to be coplanar. The workaround is to erase the surface to make it 'transparent, but quickly Sketchup will create a new surface. So it’s quite annoying and time consuming.
I have been using Sketchup for many years, but this is a new issue that has been plaguing me for the last couple of years. I also checked this on different versions and it seems to be the same issue on the older version 15.3 I still have, the current version and Sketchup Pro I used to have last year. I run the latests macOS10.13.2 on a 2.6ghz i5 with 8 gigs of ram.
Do other Mac users have this issue? Is there a preference that I selected mistakenly? Thank you for your time