The priority status is associated to the tag number in the system. The loaders will unload your bags from the BSL flight and feed all transit bags into the sorting system at FRA. FOrm there it gets sent to the container loading point for the 4Y longhaul flight. The reason for the misconnects in FRA is the staff shortage to load/unload bags from the aircraft. If the bags reach the sorting system late, it may miss the connection. Priority tags won't make a difference. If the bag missconnects it gets reassigned to the next possible flight automatically and delivered to that flight when its time comes. The recent images you saw in the media is such parked baggage outside the system because the system can only store so many bags to hold for the next days.