Timeline Viewer: Synchronisation dialog broken

If I try to synchronise videos on a Timeline the videos in the sync dialog do not show up (see screenshot below). This is the case in the current live version for the hfmdk, but not hzt/dshs. I guess it has something to do with the (post-annotator) update that we already rolled out for them. The problem also exists in current beta (and dev branches). There is no error in the console, rather it seems as if the objects are fetched but not displayed correctly. Maybe linked to showing the skeletons while loading?