Factorio Forums

As the above picture shows, there are two open blocks in the stacker where my iron ore train can park, but for some reason it refuses to choose either block and waits on the main line, jamming traffic until either that lane opens up or I force a repath by breaking the track. I'm not sure what causes this to happen, as it doesn't always jam up, but it does happen often enough to be a problem. Note that the top four stations in the stacker are for iron ore and the bottom four are for copper ore; when I alternated the stations I saw the same problem.

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The cause is simple, when it last calculated its path, the station it is targeting was the fastest to reach, now it is not, but the train did not re-path since then.