NavMesh generation should not care for Actors that are hidden in the Editor.

The problem is that the Cube is still loaded but "HiddenEd". It's AActor::bHiddenEdLayer property is set to true by the WorldPartition System. The Actor is dirty which makes the WP system pin it (won't get destroyed) until the level is saved.

Saving the level does result in proper navmesh generation in the current session but the saved nav mesh is incorrect... 

The NavMesh generation code should probably ignore actors if AActor::IsHiddenEd()  is true. 

• Create a new WP based level
• Add a DataLayer
• Create a NavMeshBoundsVolume
• Add a Cube to the scene
• Set the NavMesh to display ('p')
• The cube should affect the navMesh
• Select the Cube and Add it to the DataLayer 
  • Right-click on the DL and select "Add Selected Actor(s) to Selected Data Layer(s)"
• Unload the DL
• The navmesh is still affected by the Cube.