I didn't put the code because I would have to guess which is the code that is giving the problem and in fact it doesn't exist, the important thing for me was to understand the logic of why I was throwing that error, since the way to change the scene is with a simple changesceneto and as additional data I indicated that I am using preload() to load the elements of the scene. But you gave me an interesting fact, all that information you just gave me is extremely useful, and that makes me have another doubt:
I thought that when you use preload what I was doing was preloading those elements before loading the scene, but using changescene or queuefree would free them from memory, but from what you tell me and I think I understood it means that the elements are never removed from memory right? so of course, I want to go back to the same scene that uses preload and Godot says "hey, what's up? I loaded it before" is that right?
Let me do the test then, I'll try to change preload() to load() and see what happens.
Edit: I already tried changing again to change preload() by load() and nothing, same for testing I omit the part of the Background Loading, that is I remove the loading screen to load the level directly and thus discard that it was for the Background Loading.
Nothing, it still gives the same error and all the fault is in this line:
export(PackedScene) var next_level : PackedScene
When you click on a button you go to the level saved in next_level, but if in level 2 I indicate to return to level 1 the game throws that cyclic loading failure at the very beginning...
I edit for the second time: I already made sense of it. Indeed, it had nothing to do with Background Loading and moreover, it had nothing to do with using load() or preload(), it was indeed that line, that export:
When exporting level 2 in level 1, it loads level 2 when loading level 1, which in turn loads level 2 and thus repeats itself to infinity, so that in the export the preload seems to be implicit. If I put a simple String and pass the route works great and the problem is solved.