Identical metadata, various effects.

[frogi16]

Hello everyone, I use Calibre for over half year and I think I know something about this. Recently I added two books to my Calibre library and set their metadata. These books are of the same series so metadata are identical except title and number of part of cycle. But my ebook reader correctly show first book (everything, title, author, series, cover etc.) and incorrectly second (title is showed, but that's all). I'm pretty sure everything was set similar, I embedded metadata to both ebooks and sent them to the device.
What's wrong?

Thanks for the all replies,
frogi16