During the walk along the route I found this area that triggers the game to close the session. It is located near the Grangetown train station on and under a bridge. The trigger is best reproduced on the bridge, below it you have to walk close to the wall. tracks leading over the bridge shooting position to previous image foot path below the bridge
This fault has been carried over into the preserved collection. I still hope it gets fixed eventually within the next 24 months ...
