- When you place a blueprint that has a signal in the exact same position and orientation as an existing signal marked for deconstruction, the ghost signal isn't placed. This happens for regular-on-regular and chain-on-chain signals, but if you are replacing a regular signal with chain or vice versa it works correctly.
- When you try to place a blueprint that has a signal in the same position and DIFFERENT orientation as an existing signal marked for deconstruction, the blueprint placing is blocked and shift-placing does not place the ghost signal (as if the signal wasn't marked for deconstruction). No other marked-for-deconstruction items block the signal.
- If the signals are in the same orientation, the blueprint is also blocked if you try to put the blueprinted signal one tile above or behind the deconstructed signal along the rail. (These are the two positions that are normally blocked by a signal.) If the signal is one tile away in any other direction it works correctly.
The complicated issue: When you try to place a blueprint like the one shown below, one of the curved rails doesn't get placed. The rail isn't red and the blueprint isn't blocked, it just silently fails to appear. However, if you place it in the exact same place again, the rail does get placed! My first guess was that it's because some of the straight vertical rails are un-marked for deconstruction by the blueprint (confusing behavior, since every other entity just gets a ghost underneath the deconstructed entity when you do that). However, if I re-mark them for deconstruction after the first click, the second click still places all the rails. The behavior is the same with shift held or not.
This is the blueprint I used. You place the blueprint, let bots build it, mark it for deconstruction (and don't let the bots remove it), then place the same blueprint one track-width lower. The exact blueprint didn't seem to matter, you can even have more curves with different spacing and you can add signals and the problem will still happen, but it happens only when you have a curve and the vertical tracks next to the curve.
Here is right before placing the blueprint. All the tracks are green, indicating they will be placed (I am not holding shift).
Right after placing the blueprint once, most of the tracks are now blue but the top half of every curve that had an adjacent vertical segment is still green, indicating those ghosts weren't placed. (The color is correct, they weren't placed, but I didn't get a screenshot of it without the blueprint there.)
After placing the same blueprint again, everything is placed correctly.
This was very confusing to reproduce, so I hope it is not confusing to read. Thanks for the great game!