I had this problem after upgrading a project to UE5.2. The message would appear even though I hadn’t altered the landscape or any part of the map. For anyone who, like me, was just using the default map that comes with a new project and found the above answers didn’t work, the easiest solution is to:
- Create a new project in your current engine version
- Save the default map that’s created when you open the project
- Right click on the map in the content browser and then select “Migrate”
- Migrate the map into your existing project
- Open your original project and copy over any actors you had in the original map, along with changes to the level blueprint and references to the map asset.
That should leave you with a warning-free version of the default map, assuming you don’t have a lot of landscape changes you need to start over with.