At least I think it's a bug! I se all my elements to loop infinitely, and every element has a last keyframe at the same point on the timeline (at 20:00 seconds, in this case). Maybe every element ALSO has to have a key frame at the very beginning of the timeline?
Otherwise, if I am doing everything correctly, there is a bug in the animated ad looping process. The ad goes all the way through once and looks good. But when it begins to loop, the elements seem to display out of chronology, and choppily, and some elements don't display at all on the second go around.
I can send in the files I'm working with if that helps.