Can’t see anything wrong with your the data for the 319 route. Are you sure it was added earlier than the 519? Otherwise I would say it’s just a delay in updating (or failure to update at all) of öpnvkarte. It was supposed to be re-hosted on better servers I had heard, but I don’t know.
There’s a new transport map run by the same guy who does OpenCycleMap. This server chugs along pretty slowly sometimes. I had to request this area, then come back later to see the tiles rendered, but look! The 319 route!:
http://opencyclemap.org/?zoom=16&lat=50.9894&lon=-4.47381&layers=0B