While testing in //UE4/Release-4.16 CL 3466753 in Binary – I encountered an issue when deleting NavMeshBoundsVolume and RecastNavMesh. The NavMeshBoundsVolume is deleted but the RecastNavMesh remains.
This issue also occurs in //UE4/Main and //UE4/Release-4.15
MeshBoundsVolume is deleted, but RecastNaveMesh remains.
MeshBoundsVolume and RecastNaveMesh are deleted without error or warnings.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-45566 in the post.