When there is a navblue update. I always use the Navigraph app to remove their navdata first. Then have the sim update the navblue data. Once that’s done, use the Navigraph installer to install their navdata back.
That way the sim updates the unmodded navdata first and the Navigraph will place itself on top of it. Otherwise the navdata would update on your modded Navigraph and when you use Navigraph to uninstall it also removes the update with it. Which may cause you missing your navdata.