"set invalid index on array" warning, but it's only a problem in the build

[fen.ratskill (Fen)]

I’m prototyping a game using Blueprints and having issues but only with my build/playing in “standalone” mode. Basically, when playing in the editor I can add items to the inventory but when playing in “standalone” I can’t. I get an “attempted to set an invalid index on array inventory [-1/11]!” warning. Below is the blueprint where I set the array elements…but I’m not sure this is what the problem is since it works in the editor and I get no errors. Any ideas on how I can go about solving this? Or maybe I’m missing something obvious (not a programmer, just a designer trying to get the idea prototyped).

Close up:

[ClockworkOcean]

Do you have errors in the log during play in editor?

[fen.ratskill (Fen)]

Nope, no errors and this warning does not show up.

[fen.ratskill (Fen)]

If someone ends up here with the same problem…I had the same issue as the linked post. I needed to promote to variable rather than make a new slot structure,

Code works in Editor, not stand alone

Hey guys I need some help around something that seemed really simple… so I’m trying to find an empty element of an array and it works when I play in editor, but when I play as standalone game it doesn’t work (same occurs in the package). Any ideas why? [290558-towercraftproto-unreal-editor-10-20-2019-4-12-35-p.jpg] [290559-towercraftproto-in-editor.jpg] [290560-towercraftproto-standalone-game.jpg]