@karel Is it no-repro though? I think that the answer saying "use boot repair to solve the problem" is an answer, admittedly a bad one, but still an answer. I don't think that this makes the question a no-repro.
@technastic_tc I downvoted, left a comment and flagged the answer (not sure if flagging is 100% the appropriate action), since the OP said that they have already tried it.