Train ghosts need a bit of precision in placing them, despite the image showing them snapping to rails. Since the image of the train shows it snapping to the rail, you'd expect that clicking at that spot will place a ghost at that spot. However, the game detects the mouse pointer location, and if it isn't actually ON TOP of the rail itself, it gives an error telling you "Train ghosts must be built on rails".
Now, you cannot see my pointer in these screenshots, but the pointer is immediately above the title of the blueprint "Train liquid 1-2". In fact, looking at it, it seems that I timed it perfectly such that the error is just above the pointer, while the blueprint name is just below. I tried this with the pointer above the rail:
And below it:
I had to put the pointer directly on the rail:
For the ghost to be placed:
I expect that if the game snaps the ghost to the rail for me, that it would then allow me to place the blueprint. It should not require the pointer to be directly on the rail once the image snaps to the rail.
