NavMesh accelerating my balding

Hi all! I’m curious if I’m missing something huge in 5.6. On a new project, on a new level with a floor and a NavMesh, the NavMesh works (I know, great start). However, if I build all levels, the navmesh completely breaks and I get an error that it needs to be rebuilt. Rebuilding doesn’t do anything. The only way to get it back is to reload the level, or to delete and regenerate the RecastNavMesh.

It’s also important to note that on the default big empty map, the navmesh works fine after building all levels. Is this because it’s using world partition? Do I need to change a default setting? I’m not sure if I’m just dumb and am missing something critical to how navmesh works in 5.6, or if it’s a much bigger bug. Would incredibly appreciate anyone who can help me understand this.