Several years ago I was puzzled. Books in my library (the file - not the entry) would "disappear". It took a while to figure out - and it was the result of the naming of the files - and my accessing the database from different operating systems. The problem came when I loaded a book on a Mac or Unix system - but tried to access it on a PC.
I hope someone can help me SET a universal naming system on any of my Calibre installs that will be compatible with the Windows OS for future entries. And to take existing libraries created on a Mac or Unix system and bulk rename them to that system now.
It seems like this should be achievable - but I am just not expert enough in this area to figure it out. (Although I said this back when I first recognized this - I would love to see a SETTING in Calibre that would be a simple click to tell any install to use a Windows compatible naming protocol for users who don't understand this.
Anyhow - any help would be greatly appreciated.