Funky pedestrian routing in conjunction with ferries

[buttercookie42]

E.g. https://valhalla.openstreetmap.de/directions?profile=pedestrian&wps=-1.0601806640625002%2C50.81114153614715%2C-0.37490844726562506%2C49.18170338770663 gives some very strange routing between the port and Caen city centre:

If I move the start to Brighton, the routing in Caen fixes itself, but instead there are weird detours in the Portsmouth area:

[nilsnolde]

dup of https://github.com/valhalla/valhalla/issues/3941 :)