Factorio Forums

I have several blueprinted train intersections and I have noticed that when placing some of them from a blueprint, after building there are some signals that are flashing even though they are in legal positions. I actually noticed a bug similar to this one in 0.12 that was resolved in the 0.13 update when placing by hand, but it appears to not be the case when building by construction robot.

Basically when there is a signal in the closest position of a merge between a curve and a diagonal rail, it works fine when built by hand. However when built by a construction robot about 50% of the time the train signal will flash to indicate that it is in an illegal position even though it is not.. If deconstructed and rebuilt by hand it then works fine.


This is the simplest blueprint I made when I could consistently get flashing signals on one or both of the circled signals.


Attached is a save of a map with 2 problematic blueprints in the hotbar so you to try it out yurselfs!

It might be related to the construction order, rather than bots specifically - I've seen flashing signals when hand building too.

- Place one path of the junction. Plan, but don't place, the other path
- Place a signal at the point that will be the closest valid point to a junction
- Place the other path of the junction

The signal now flashes as if an invalid placement

- Remove and replace the signal at the same location - all is now good.

Thanks for the report,

I have managed to reproduce the bug