Hello, I have been using Navigator App with the free OSM maps for some years now and the biggest problems I find are related to the OSM information. One of them that I detected is the difficulty to distinguish between paved roads and unpaved roads. Unpaved roads don't have any different colour on Navigator App Map representation, and there isn't an option on Route Setup to config unpaved roads so I could avoid them.
from my experience, this is what I see in navigagor:
"highway=motorway|primary|secondary etc" are displayed in white color (in OSM terminology means general "road" typically with asphalt, but can be different surface).
"highway=track" are in grey color (in OSM this is usually road not for general traffic, like forest road or field road, more often unpaved or only with gravel etc...).
I do not know how is highway=road displayed but according OSM wiki this is unidentified road so preferably should not be used.
I had this dilemma with some road and in the end after going through OSM wiki I changed it to "track" type.
It is rather uncommon to have really official "road" (highway tag in OSM) that would be unpaved. So maybe the maps should be corrected in the problematic area? I'm not saying they should be changed to work better in this particular app, but maybe they are not up-to standard (see OSM wiki)
The other thing as you mention would be nice to have a switch to allow or block unpaved roads. I only see a switch for "small local roads" which I have no idea what exactly is, which tags from OSM are included here. I would think those could be tracks. The question is whether Navigator looks at the surface tags. (I havea feeling it does not, after some experimenting...)
May i ask you from where you are? Could it be a general OSM classification problem? (paths and tracks tagged as unclassified roads) Are you involved in mapping?