Major How to reproduce
I insert the search service.
I choose the search on content types : articles, news and multimedia contents (audio, photo, video)
I choose facets on content types.
I choose content types and page's title as criteria.
Behavior
When doing a search with "article" as criteria, the search returns article, about and my favorites contents (see screenshot)
This is not a bug, this is the desired behavior. You are searching pages which contains at least a content with the type 'Article'. The page 'Liste de liens' matches this serch, and this page contains two contents : one 'Article' and one 'Link list'. So as a result, you got the facet value 'Link list'.