How to reproduce

• create page
• create article tagged News
• create article tagged Conferences
• add a content digest
• choose the tag News
  => both of the articles show

Now, set the content digest and choose both of the tags News and Conferences
=> you only get the article tagged Conferences whereas you should see the other one too.

=>> I think the problem is that the service looks for contents that are tagged with tag1 AND tag2 while it should look for tag1 OR tag2