update library errors

Arghhh…driving me mad. When I add a video source, lets say TV for instance and I select TVDB to catalog it, its all good. When videos get added to that folder and I do update library, it doesnt add new videos to the relevant tb shows. It makes a new tv show called “internet sluts” and all new episodes appear under it. The only way I can add properly is to go back and select a different catalog service like xem and it will sort it out properly again.

Any ideas?