I have a World Composition setup with a persistent level and 4 landscape levels. I set up navmesh bounding volumes in each area, then load the levels and build the navmesh. The green area does not show up in game and AIMoveTo fails with aborted. When the levels are loaded by hand in the editor, the green area shows up perfectly, only not in game
I found a workaround to this.
All you have to do is place one navmesh volume in the persistent level. It does not even need to encompass any geometry. Just placing a simple volume in the persistent level makes the navmesh show up in all levels.
I think this must be a bug and I will report it as such.
Hopefully this post will help somebody with similar problems
EDIT: I triumphed too early. The above solution works but only during the session in which you create the navmesh from the build menu. When you exit the client and restart it, everything is gone.
The only solution seems to be that the navmesh volumes must be in the persistent level.
Whether this is by design or not, the fact that the green navigation data exists during a session and does not exist anymore after editor restart looks like a bug to me