Factorio Forums

Simple steps to reproduce:

0. Have a personal roboport with construction robots, disable the roboport using the toolbar, and be standing outside a logsitics/construction zone before starting.

1. Place some obstacle - train tracks are what I used.

2. Mark the obstacle for deconstruction. At this time nothing will actually happen since no construction robots are available.

3. Place a belt and underground belt that jumps over the obstacle. Keep holding down the mouse button and hold the mouse still.

4. Enable your personal roboport by keystroke (Alt+R by default). This should eliminate the obstacle.

5. Place belts over where the obstacle was, either by walking or moving the mouse.

This will place additional underground belts, which is not only unnecessary but the new belts are pointing in invalid directions and could not be connected to each other. The results of step 5 renders the overall belt obstructed and unusable.

I suppose these could also be performed in multiplayer if another player removed the obstacle, but I have not tried that.

Looks like I managed to do it without an obstacle: 94375.

But it can be a slightly different code path since you don't release the button and I start building over existing belts.

I feel like there's something different here. If you look at my screeenshot you can see one of the underground belts is actually moving material to the left even though the belt was built going right. My guess is it saw the start-end points moving leftwards because of how I moved my mouse, so the "input" underground points left, but the "output" points right.

This is generally part of the problem of respectiving underground belt gap when build dragging belts, which is now resloved for 1.1.12