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asw22 - what OS are you using (Windows, MacOS or Linux)?
What is the path to your library folder?
By default Windows auto-syncs the Desktop, Documents and Pictures to Onedrive. I think that started within the past ten years. It's best to keep calibre library folders well clear of those locations - e.g my libraries have paths such as:
Code:
D:\Calibre\Libraries\Books
C:\Users\xxxxxxxx\CalibreLibrary.
BR