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I'm out building mines from a huge blueprint. I place down the blueprint, including rows of miners, belts, and inserters and rail and stop for the trains. It also includes four roboports to get it built. Then, I hand place one roboport and a supply chest, then fill them with the bots and materials. When it's all done building, I remove by hand the roboports and the supply chest. And now I have more roboports than I started with.

Roboports are not automated in the factory and I am going for the lazy achievement so haven't accidentally built any by hand. I have no roboports placed in the world other than the ones I place temporarily for building. I have no larger logistics network and no logistics bots. Checking the all time production statistics, 20 roboports have been built. 10 were used to build personal roboports, currently on me. I went out with a stack of 10 roboports to work with. And now I have 15 roboports in inventory. It doesn't happen every single time, I've built maybe 20 or 30 mines like this and it has duplicated only 5 times.

It's possible the new roboports don't appear immediately but instead sometime during saving and loading the game.

I am on experimental 2.1.12 - with no mods other than the space age ones.



-edit-

Personal roboports don't use roboports as a input I forgot. Ignore mention of them. 10 Roboports are stored in a box in the base. 15 were in my inventory, starts show 20 were built total.


Since then, it happened again. I built 2 more mines using blueprints, then removed roboports. I now have 16 roboports in inventory. 10 still in box at base. 20 total were made in statistics. Can rule out saving and reloading, no save and reload was done between 15 and 16 in inventory.

Post the save and exact steps to reproduce the issue with please, see 3638.

Here are attachments.

startx23 file a save before (duplication had already happened I think 5 times). Character has 15 roboports in inventory, 10 more are in a box in the base. No active production of roboports ongoing.
startx24 save after more recent duplications. Character now has 17 roboports in inventory, 10 still in box. No production, production stats have not gone up.


Steps that led to this.

-turn off character personal roboport
-place large mining blueprint (only blueprint in character inventory with miners) includes miners, belts, inserters, rail, and train stop
-place by hand one of the roboports, placing over the blueprinted one
-place by hand a storage chest
-hook up roboport to power
-fill storage chest with materials and roboport with construction bots
-allow construction to occur (maybe not the whole mine, maybe only the other roboports)
-once construction is done, pick up the roboports (filled with construction bots, no bots currently floating waiting or recharging) and pick up the storage chests.


Duplication doesn't seem to happen every time. Happens maybe one out of 4 times.

Some further experimentation

I tried using a new small blueprint with just four roboports and storage chests. I attempted several times using the same steps with this smaller blueprint and didn't get it to happen.

And I tried another small blueprint of four roboports with also some track and train stop and this also didn't seem to cause it.

So maybe it only happens when there is a larger construction blueprint, or if more time and player actions occur between placing and picking up the roboports.

Thanks for the report. After couple of tries i was able to reproduce the issue using provided save file and provided steps. It is now fixed for 2.1.13.

Issue was a weird interaction caused by lua even guard in case building a roboport invalidates the construction robot, however in this case when construction robot built a roboport, the logistic network was merged between existing roboport and one just built and this caused construction robot to migrate to a new network. This migration to new network was flawed making this lua event guard trip incorrectly causing revive logic to abort right after roboport was placed but before item was consumed which is why you observed the item duplication.

boskid wrote: Fri Jul 31, 2026 8:06 pm It is now fixed for 2.1.13.

Hey awesome thanks that was super quick ha ha! I was actually just coming here to report that I actually haven't been able to get it to happen again since porting this. Glad you were able to figure it out!