It would be interesting to find out what has happened. You are quite right, this seems very strange.
Something is very, very wrong. I believe that the next thing to test is to uninstall and delete everything relating to Calibre and then start from scratch.
Either your computer is f****p or you have somehow inadvertently corrupted the Calibre Library and/or the meta data database.
Caliber is perfectly able to sort on Author, unless it has been broken.
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