I know this is a old thread, but "FindGameObject" action does still have a similar issue if the tag is not defined (UnityException: Tag: 00-10 is not defined.)
So if you want to find a gameobject by a tag which does not exist in unity's tag-list, this action will not call finish. It even blocks the current state, following actions will never be executed.
Maybe it's not the best idea to search for not existings tags, but I need this in my special case (many different numbered tags and objects, found objects by tag will be stored in array).