After navigating to destination, start menu item is disabled

Question

I have a single activity class with 2 fragments, both at the top level of my navigation hierarchy. Both fragments are connected to destinations, and they are shown in my navigation menu.

Other than the standard navigation menu, in fragment1 I have a custom button associated to an action for navigating to fragment2, without arguments nor state to be remembered.

This works fine, including the standard back navigation to fragment1 using the standard back functionality.

The problem is that after navigating using the custom button, the menu item to fragment1 is disabled. How can I restore it?

Code managing navigation from custom button in fragment1:

findNavController().navigate(HomeFragmentDirections.navFrag1toFrag2())

NavigationGraph.xml

<navigation xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/nav_graph"
  android:label="@string/frag1"
  app:startDestination="@id/nav_frag1">

    <fragment
        android:id="@+id/navigation_home"
        android:name="com.perissf.Fragment1"
        android:label="@string/app_name" >
        <action
            android:id="@+id/navFrag1toFrag2"
            app:destination="@id/nav_frag2" />
    </fragment>
    <fragment
        android:id="@+id/nav_frag2"
        android:name="com.perissf.Frag2"
        android:label="@string/frag2" />
</navigation>