Loading a Map variable from a save file returns Unknown after a restart

Before you ask I’ve already seen this topic and did not undersatnd anything.

UE5.3.
I’m trying to load my inventory items. Inventory consists of ItemObject (parent Object) and it’s child objects. It is based on this tutorial: Spatial Inventory Tutorial

Tree of ItemObjects:

 ItemObject
 |
  --- Consumable
 |
  --- Key
 |
  --- Stackable
         |
          --- Ammo
         |
          --- Weapon

This is how i save those objects:


P.S. Items weren’t separated to Normal and Stackable before. You will see why.

When I try to load on the same gaming session, everything loads perfectly.
But when I close the session, restart the game and try to load… Stackable objects won’t load. Even when I’ve separated them.

Breakpoint on saving:

Breakpoint on loading on the same session:

Breakpoint on loading after restart:
… it crashes everytime i try to see the values of stackable items map. Here’s the values of keys on that map:

As you may have guessed ItemsMap consists of ItemObject. And StackableItemsMap consists of ItemObject_Stackable.

What should I do to load them properly?

Also
Here’s what output log says when i try to load after restart:
LogUObjectGlobals: Warning: Failed to find object 'Object None.None'