The whole concept in quantum mechanics of a particle's wave function collapsing into a single point due to an observation event is just weird enough, and feels just enough like some otherworldly programmer's hack to save tons of resources, that I am not sure I will ever be fully convinced that we are not in a simulation.
I'm not asserting that we're in one, and I don't know of any reasons to believe that we are in one, but I think I'll always have that little suspicion.
