Navigation data contained entirely within a Level Instance is not registered at runtime (PIE / standalone / packaged) in a World Partition persistent level

A licensee is composing independently-authored levels into a single World Partition persistent level by placing each as a Level Instance. NavMeshBoundsVolume / NavModifierVolume are placed inside each sub-level (Level Instance), and navigation is built at the persistent-level side. Navmesh appears correctly in the editor outliner after build, but is not available at runtime.

Steps to Reproduce

1. Prepare two World-Partition-enabled sub-levels; place NavMeshBoundsVolume + NavModifierVolume + floor mesh in each (streaming disabled).
2. Disable auto navmesh generation (Project Settings Auto Create Navigation Data = false, Editor Update Navigation Automatically = false, World Settings Auto Spawn Missing Nav Data = false).
3. Place each sub-level as a Level Instance into a WP persistent level (streaming enabled).
4. Build navigation (Static).
5. Enter PIE (or standalone / packaged) and run show navigation.

Expected Result

Navmesh built for the Level-Instance-contained NavMeshBoundsVolumes is present and registered at runtime.

Actual Result

• RecastNavMesh is visible in the outliner immediately after build, but disappears from the outliner after reopening the level.
• RegisterNavigationDataInstances() — for (TActorIterator<ANavigationData> It(World); It; ++It) — shows RecastNavMesh registered when loading in the editor, but no RecastNavMesh is registered during PIE.
• Result: built navmesh is absent at play time. In this case no duplicate RecastNavMesh occurs — zero navmesh is registered.

Workaround

Move NavMeshBoundsVolume / NavModifierVolume up to the Persistent Level.