Seems to be an issue with the landscape material. Trying to move the file causes this error
Graph is linked to private object(s)
in an external package.
Try to find the chain of references to
that object (may take some time)?
Selecting yes fails to work and then continuing/cancelling causes the map to be corrupted and trying to load the moved file causes the editor to crash.
A workaround is to move the file and then remove and readd the material (Or the other way around) in the landscape’s details before saving.
Repo for reproducing this https://github.com/SuperWig/04_BattleTank
Edit: Appears to be UE-62150