well, at least it’s not your memory lol
prototype used Godot 3.5, full game uses Godot 4.0.2, so there’s an entire rewrite in-between
the fact that the prototype worked fine does suggest to me it’s an engine problem, the code used for the startup screen absolutely was present in the prototype.
cursory searches say that error comes from C++ pointer problems, which definitely means it’s on the engine side. nothing i can do about it until it gets fixed upstream, sorry about that