Any error messages output to the console when it's failing? There's a few potential causes.
1: Godot just breaks when more than a certain number of objects added to the ScrollContainer. So maybe at around 4000 things worked, but at 6000 things just break? If so I'd expect to see some errors in the console.
2. My mod uses a bit of a hack to render the initial viewed items. Without the delay, the rendering engine hasn't setup the size/location of everything yet and so it thinks everything is visible and the delayed loading ends up loading everything. I thought the way I did it the actual delay didn't matter as it's block on that compositing, but maybe I was wrong
3. Something I'm not thinking of, but console output might help identify.
