Have you ever felt like you've been here before? Maybe you haven't. Maybe the system just failed to fetch the new asset and reloaded the old one from cache.
The Computational Argument
If it is possible to simulate a universe, and if civilizations survive long enough to build such simulations, then statistically, we are almost certainly in a simulation. There is one base reality, and billions of simulations.
Glitches
The Mandela Effect. Déjà vu. The weird feeling when you walk into a room and forget why. Are these bugs? Or feature flags?