Yes I had the same problem with my Sage. In the thread about the 586 firmware
https://www.mobileread.com/forums/sh...d.php?t=354942
much has been said about this nasty problem with some good advice.
What I do is a reboot of my Sage before I connect to my desktop. My ereader is therefore not in a book when I connect. I then connect with calibre and send the ebook(s) over. I eject from calibre and so far that is fine, my Sage imports the ebook(s). Other people first close calibre and then disconnect from windows.
Maybe this will help you also.