There’s a whole slew of small moments like these in Frozen, just like other movies, but most, like the sandwich error, don’t take away from the final project.
Usually those moments are small and don’t detract from the final version of the film, but they can be fun to spot when all is said and done.
In fact, continuity errors are common in movies, both animated and live action, sometimes simply because a brief moment is missed by the supervisor or because a take that is better than another is chosen simply because it is better.