After restarting the containers, it switched to 404 for a short time, then returned to 401. I have noticed that my redis and postgres containers are currently not using the latest image versions (redis 5b8f8c and postgres 32324a2), but I doubt that this causes the issues.
Container logs look normal (ending with LOG [Api:Bootstrap] Immich Server is listening on http://[::1]:2283[v1.138.1] [production]).