AS2: swapDepths - stops movieclip from moving

I have 4 cards on a carousel moving around - each card has to come to the front every time it moves around. My problem is I go to swap the depths using movieclip.swapDepth(1) and it brings it to the front but it then stops that movieclip moving on in the main time line so it stops moving back around. Does anyone know why it is doing this? I have also tried using moveiclip.getNextHighestDepth() + 1 but that does nothing!

Thanks for any help as I am stumped!