where the arrows mark one-directional track and there is exactly one more station at the end of the rails heading off the bottom-right corner, one would expect a train leaving from the Bryan Burr or Marc Jaisek stops to be capable of making its way to Paul 'Xanzibaarbarian' Cooper without much undue trouble -- it can just enter the one-directional section (the bottom of the two parallel horizontal tracks) and then branch off toward the north.
Unfortunately, what happens instead is the train ignores the branch and keeps going forward until realizing there's no path to its destination anymore. After that it stands there and shouts "No path!" at me like an idiot.
I've driven the path myself in the same train, so I'm certain it's valid (the switch is a switch, and once driven manually past it, the train is perfectly capable of reaching the Xanzibaarbarian station on its own), therefore I can only assume the track setup is too confusing for the poor thing.
The save, should you wish to poke at it, is available at http://dev.narc.ro/factorio/lousy-pathfind.zip. The train is stopped just after its recognition of its own mistake -- enter the leftmost locomotive, drive it forward a bit (towards the Bryan Burr/Marc Jaisek station complex), and then let it try again; it should make the same mistake every time. You may also verify for yourself that the Xanzibaarbarian station is perfectly reachable, though you'll have to navigate the train past the troublesome switch first.
Good luck!
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