Do you have VT enabled? I spent a day debugging this issue on 5.2 and here is what I found I also figured out how to fix this error.
VT needs to be enabled if your using HLODs or it will cause a memory leak and video memory usage will be sky high.
VT needs to be disabled when building HLODs or IsRoutingPostCompilation will return false and the build will fail.
So yep its bugged for sure, but just disable VT build your HLODs then enable it again.
You can switch out the material on the HLODs to a non VT one which will also work but I found doing the above easier for me.