I have added the series Babylon (2014) (http://trakt.tv/show/babylon-2014). sonarr just downloaded an episode of a different show with the word Babylon in it - The.Spoils.of.Babylon.S01E02.HDTV.x264-2HD. I can confirm that this is a different show. I assume it happened since the word Babylon appears in the release title.
No, title matching is much more strict, your indexer must have assigned the wrong tvrage ID to that release, so it grabbed it, It would fail to import due to the title mismatch though.
Thanks for your reply - you were exactly right.
I disabled the indexers and tested them one by one. Two downloaded the wrong release and two downloaded the right release.