Well in my opinion - the main problem with this:
PackagingResults: Error: appError called: Can’t save D:/PerforceWorkspaces/GDNBS/DES4/04/Source/KMills/NewVersion/Saved/Cooked/Windows/FP_GameGuide/Content/FirstPerson/Maps/PatientZero.umap: export (/Game/FirstPerson/Maps/PatientZero.PatientZero:PersistentLevel) has a reference to export (/Game/FirstPerson/Maps/PatientZero.PatientZero:PersistentLevel.WorldDataLayers) which still has its external package set to (/Game/ExternalActors/FirstPerson/Maps/FirstPersonMap/D/0W/E1FKEGVKGOLM7HGLQPCIPO).
May be that tell you anything, unfortunatelly I don’t know how to solve it. But I’d try to delete “Intermediate” and “Saved” folders in your project folder then try again
