It's possible for NaniteStaticMeshesInFlight to never be decremented because all the background workers are waiting indefinitely for the ones in flight to complete their static mesh build.
set landscape.nanite.maxsimultaneousMultithreadBuilds to a non-zero value.
launch some nanite landscape builds on very large landscapes
it will eventually hang.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-220638 in the post.
| 0 | 
| Component | UE - Graphics Tools - Terrain - Landscape | 
|---|---|
| Target Fix | 5.6 | 
| Fix Commit | 39233573 | 
|---|
| Created | Jul 31, 2024 | 
|---|---|
| Resolved | May 6, 2025 | 
| Updated | May 7, 2025 |