Originally Posted by NiLuJe
@Vaesse: Next time you catch one, restart calibre in debug mode, and check how the 'on device' / 'in library' match is done... It should be by UUIID, and it should survive the plugboard. AFAICT, this doesn't have much to do with this plugin in particular, since it trusts the data Calibre feeds it, but you never know
As luck would have it... just happened again. I have verified that neither side shows the other (library does not show them on device and device does not show them in library). I also noticed (before restarting in debug mode) in the task list an error writing metadata to device.
Not sure how to tell from the log if it's using UUID or something different to "connect" books on device to books in library.
EDIT: I'm "repairing" most of the problem books, but leaving one (lengthy) series unfixed so I can continue to try to alive this issue.