Book not showing in filtered combine page

[lethe]

https://www.goodreads.com/series/1798...

All 3 of the books in this series are visible in the combine page when I filter on 'livre', but when I filter on 'north' or 'northlanders' only tome 2 and 3 show up, Le Livre anglo-saxon does not.

Maybe this belongs in the Feedback Group rather than here, but I may also be missing something obvious?

[Arenda]

When I merged a duplicate of the French edition of book 1, only one of them showed when filtering on "north".

[Renske]

I have noticed that issue also several times. There is a thread in the Feedback group https://www.goodreads.com/topic/show/...

[lethe]

Thanks, have posted my example there.