Factorio Forums

What did you do?
Placed Elevated Rails, then tried to force-build a blueprint of other Elevated Rails over the top.

What happened?
Bots replaced some of the rails, but got permanently stuck on others.

What did you expect to happen instead?
Bots should have removed all in-the-way entities and built the entire blueprint.

Does it happen always, once, or sometimes?
Always

Detailed explanation / reproduction:
The attached save is in sandbox mode but the problem occurs in freeplay too.
The save has a Roboport, a storage chest and some pre-existing (straight) elevated rails that I placed.
In the Game Blueprints there is a blueprint for an elevated T-junction.
There are 50 Construction bots in the Roboport and enough materials in the storage chest to build the T-junction outright.
Take the blueprint, align 2 of the Elevated Rail supports from the blueprint with 2 of the existing supports, then move the cursor down such that the new supports are offset from the existing supports. Force-build. This will mark the old supports for destruction and ghost the new supports. The bots will fly out to do their thing but some of them will go to their target and just hover in place. Forever. Some of the entities marked for destruction will never get removed - even though there are idle bots in the Roboport.

I think what is happening is there are some elevated rails that aren't marked for destruction, and so the supports underneath them can't be removed. But until they are removed, the new entities cannot be placed down. So the bots with the new items are waiting for space to deploy but nobody is coming to remove the existing supports until the supports are no longer needed (which never happens).

I think the solution should be that, if a rail support is marked for destruction, then the rails above it that require support should automatically be marked for destruction too and re-ghosted so that they will be restored automatically if/when a new support is built. If the player intends to remove the elevated rails too then they can simply clear the ghost after.

Related threads:
viewtopic.php?p=694684
viewtopic.php?p=676290

I don't think this is entirely a duplicate - this specifically relates to bots. The bots hovering in place and holding on to the items forever and no bots coming to remove the entities marked for destruction.

It's a duplicate because force-pasting blueprints that shift elevated rail supports without first deconstructing *everything* they are attached to is considered an unsupported action. The game is simply not programmed to figure out on its own that in order to remove the marked supports, a bunch of unmarked rails would have to be removed and then replaced in the same spot after the new supports are built. You have to do that manually before placing the new blueprint.

Bots hovering forever waiting for space/support to build their thing is just how they work. And bots won't dispatch to deconstruct a support until everything it is supporting is gone (they used to do this, and would get stuck because there were no bots left to deconstruct the track.)

Maybe so, but destructing a support implies destructing the rails and so should be automatic. The bot logic is "I can't remove the support until the rails are gone, so I won't try" - great! Take the rails then.