Paperwhite books vanished from collections
Some books that I have in Calibre I decided to reconvert so that I could include the metadata. When I transferred these to my PW (without deleting them first) they vanished from their collections and also did not appear after the collections in 'collection' view. They did show up in the other views, 'title's and so on, but I could not make them appear in the original collections. The count of books in these showed 2, for example to include a missing book, but only one old book was listed. Even a hard reset did not fix it. Eventually I deleted the collections, re-added them and then added all of the books, and this worked.
This did not happen with my old Kindle Keyboard, so is it only a PW issue? I guess next time I will delete from the PW before re-copying over.