I get build fails and now do this to get around it.
Make a new HLOD layer in Content Browser
Delete old HLOD layer, replace references to new HLOD layer, DON’T save …
Build Landscape
Double click level thumbnail in Content Browser
Build HLODs
Launch Session.
But latest update is triggering validation fix messages on Launch, still builds HLODs and load into the play/edit session, but on UEFN side the new fix button is not working… about to do Jimbohalo10’s suggestion here