Pasting an instanced subobject property into a Blueprint prevents that Blueprint from being added to level

Copying and pasting an array of nested instanced subobjects from a level instance into a Blueprint's defaults and adding that Blueprint to the level will prevent the actor instance from saving.

• Open attached project (Built at CL#23115094 Release-5.1)
• drag an instance of /Game/B_AddMeToLevel into the level
• Save the level
• Note the error "Can't save ExternalActors/NewMap/*.uasset: Graph is linked to external private object */Game/B_AddMeToLevel.Default_B_AddMeToLevel_C:MyParentObject_1 (Referenced because it is an archetype object)"