I realize you’re nearing the end of your project, but you might want to look into ResourceLoader
I have a hunch you might be attempting to access something before it’s done loading. Resources tend to load almost instantly locally but then once they’re “out in the wild” it takes more time to load them into your project, which can expose logic that only works locally. Again, just a guess… I made a video on a more robust way to load scenes which you can watch here if you’d like. Bear in mind, it’s written for Godot 4, but the concepts are the same even if the code can’t be copy/pasted into your project.