The whole enterprise is foolish. If there were really such contradictions, then there would be some failure to predict experiments.
Scott Aaronson pauses from his agony of being a Jewish leftist Trump-hating professor in a red state to explain:
So: a bunch of people asked for my reaction to the new Nature Communications paper by Daniela Frauchiger and Renato Renner, provocatively titled “Quantum theory cannot consistently describe the use of itself.” Here’s the abstract:The paper authors separately argue that this proves the many-world interpretation.Quantum theory provides an extremely accurate description of fundamental processes in physics. It thus seems likely that the theory is applicable beyond the, mostly microscopic, domain in which it has been tested experimentally. Here, we propose a Gedankenexperiment to investigate the question whether quantum theory can, in principle, have universal validity. The idea is that, if the answer was yes, it must be possible to employ quantum theory to model complex systems that include agents who are themselves using quantum theory. Analysing the experiment under this presumption, we find that one agent, upon observing a particular measurement outcome, must conclude that another agent has predicted the opposite outcome with certainty. The agents’ conclusions, although all derived within quantum theory, are thus inconsistent. This indicates that quantum theory cannot be extrapolated to complex systems, at least not in a straightforward manner.
That conclusion should be enuf to dispose of the argument. The MWI does not predict any experimental outcomes. There is nothing scientific about it. It is like some solipsist saying anything can happen in his imagination.
Aaronson explains the errors in more detail. So does Lubos Motl. Somehow this paper got published in a Nature journal. It has become respectable to trash quantum mechanics with silly arguments.