Originally Posted by intipuss
It's simply as I said.
I add a book to Calibre and it's on the Kobo with all info/metadata.
I add another book from the Calibre library to my Kobo and as soon as thats added you can see & watch the green tick disappearing from another that you previously had on the library. I checked the Kobo after disconnecting it properly - the new book is there and the 'deticked' book has gone. I found some of the 'disappeared' in seperate folders in Kobo - although all info was there previously ( author, title etc) and now its showing up in these folders as title unknown/author unknown.
Many thanks for everyones help, but I have now given up with calibre and moved on EPUBOR Ultimate which although has no library as such, allows me to convert the books to EPub and they don't delete.
The shame is that you did not seem to want to work with people here to track down the issue.