Hello Sean!
Yes, It is reproduced in a clean project.
steps i follow:
-create a new project
-create a floor, just a simple box
-create a nav mesh bounds volume, and extend it.
-create a nav modifier volume, and from nav modifier volume’s details panel create new nav area, and from its properties, set any draw color.
-place the nav modifier volume inside nav mesh bounds.
When completed, nav modifier wont effect the world or draw the color it is supposed to. Only solved by restarting the engine as far as i see. Using one of the Defaultly created nav areas however works fine