[0.13.17] Train won't find path with signal only on one side

[Cutemine]

See this screenshot:

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The train tying to go from the left to the right station on automatic mode has no trouble, but in reverse it won't find a way. Adding a signal on the opposite of the existing one at the white indicated spot fixes the problem, but I'm not sure if this behavior is intended. Moreover, adding a signal slightly diagonally on the other green indicated spot breaks the path from both sides and also makes it impossible to place a signal on the correct spot without removing the wrong one first. It's therefore hard to spot the error. The problem also happens on strait track, but is much easier to see there.

The safefile is attached below.

Win10, 64bit, Factorio 0.13.17, no mods

[Loewchen]

Well, if you only have a signal on one side it means the train can only go in that direction.
NaB.

[Cutemine]

Well then the second possible place to put the signal is kind of pointless, unless you somehow want to break your paths in both directions. It should then not be possible to place an of-by-one signal after the signal on the other side is placed.

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The position with the red arrow should not be offered as possible placement if it breaks the paths, however the other side is correctly not present.