When opening the savegame, you see a train reversing at the station and another train approaching it far away (outside of image). The oncoming train has a directional reservation up to the choose signal as should be. When the stationary train is done reversing, it will make a directional reservation as far as possible, in this case up to the back of the choose signal, rendering a deadlock. All signals use timeinterval with telegraph. If you look around the map, you will see a bunch of trains in that deadlock state.
savegame: http://server.exp.simutrans.com/debug-saves/directional_reservation_reserves_even_though_the_entire_path_is_not_free.sve (http://server.exp.simutrans.com/debug-saves/directional_reservation_reserves_even_though_the_entire_path_is_not_free.sve)
pakset: Swedish pakset with this commit: f820a2ff3495b1e4f7dde674da5ef050b3ad3834
Thank you for the report - I think that I have managed to fix this. Would you be able to re-test?
Yes, it appears to work correctly now! Thanks!