Hi Fabien,
Thank you for the details, it helps us a lot!
The taxonomy connection logic in this case does not apply, as all the terms are within the same taxonomy (category). That means, that ‘Marques’, ‘Gamme’ etc.. are not actually separate filter groups, but simply a part of the same exact, single category filter.
When unchecking everything in under the ‘Gamme’ main category, but ‘Semi-professionale’ has no effect on the items, that are not marked with any of the categories within the ‘Gamme’ category subset.
Say, you uncheck ‘Professionelle’. Then anything marked with that category will be excluded. There are however items, that are not marked with that category, but marked with something else. On those, this has no effect, since it is the same filter group.
The only solution here, is to separate these items into different taxonomies, so that separate filters are created for them automatically, and the taxonomy logic then will apply on them. In that case, unchecking something under ‘Gamme’ will be separately queried, as well as all the other filters.
I hope this helps!