Layout odd behavior: hatch visibility problem

I am having an odd problem with Layout. I have a file that contains the plans for a school I am designing (I put the sections and elevations in another file so that the plan file did not get too big). all the plans but one show correctly the hatches and black lines. in just one plan the black lines show in gray. the elements in this plan are the same as in the others, rendering mode is the same (hybrid) but I cannot seem to be able to put this right.

in Sketchup everything looks great but in Layout I get this problem. when I export the file to pdf the problem is still there. I am using the high setting when exporting to pdf.

I hope you someone has a suggestion for things to check.

thanks.

As it appears in Sketchup

As it appears in Layout

As it appears in pdf