The plug-in cannot determine which instance should be restored.
You have to, besides using the “Procedural” interface, implement a guid property called “SGUID” on actor class and give each instance an unique value to the SGUID property at spawn time.
The level 3 on demo project uses actors spawned at runtime as example.
If guid values are correct then it’s a matter that, when array is restored, actors with corresponding SGUID didn’t finished spawning yet so the array do not restore references to them.
If the case is this, it’s possible to call “Load Actor” again from the slot instance once everything finished spawning.