I have Calibre Companion on my first gen Kindle HD and love it! Today I went to add 174 books to the device (which would make it a total of 645 books on my device
) and everything seemed fine, there were no error messages, but there was one book in my Calibre library that didn't have a check mark in the On Device column. So I tried to copy it over again and the dialog in Calibre and Calibre Companion showed it copied over (again no errors), but once again the check mark didn't appear in Calibre and the book wasn't listed in CC. When I closed CC, the book was in my carousel. I decided to go ahead and restart my Kindle. The book was still in the carousel but not listed in CC.
I decided to delete the book from my device and try to load it again. Again no error messages (just the usual dialog), and this time the book appeared in CC and was check-marked in Calibre, but another book got uncheck-marked in Calibre and disappeared from Calibre. When I loaded it into CC the original book got unmarked and disappeared from Calibre (and this time didn't show up in my carousel or my book folder).
I have plenty of memory on my Kindle (24 GB out of 27GB available), so I was wondering if I somehow discovered the upper limit to the number of books that CC can manage. There are no error messages from either Calibre or CC, the books just seem to keep swapping.