Locked a portion.
That is YOUR system that has done that. You need to find out what is 'stuck' and unstick that.
An A/V action? Another process is using that file (eg. you minimized the viewer instead of QUIT).
How about a Sync app still running that include a system folder (calibre2 or a DLL) OR your Book Library? (IIRC Calibre 5 needs to restructure parts of metadata.db )
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