Every time you Play in Editor, your Game Mode blueprint will spawn your Main Character with a different Instance ID generated by the engine at runtime.
You can simply edit the SGUID manually on your Main Character blueprint and ditch the “Make SGUID” node from constructor…
Or you can change node mode to “Static Name to GUID” mode.
Verify that the SGuid value of your spawned MainCharacter blueprint is always the same every time you enter play mode.
Oh, and uncheck “Save Game” option from SGUID property if you never want it to be loaded from save file (in your case you don’t).