Originally Posted by kovidgoyal
The only other driver that manages an on device database is the sony driver. At least for the older devices (before the T1) the driver scans both the actual files and reads the device db and metadata.calibre. It then populates the metadata from those three sources. IIRC the device db has the lowest priority. So files on the device are always shown as on device regardless of their status in the device db. This has never been a problem with the SONYs as they are a lot more robust than the Kobos.
This isn't a case of lack of robustness. It is either the device hasn't had a chance to look at the book, or the device finding a problem with the book and not loading it.