Changing Assembler Speed can lead to inserters deadlocking
Posted: Wed Jun 10, 2026 2:30 pm
The maximum output an assembler crafts to depends on its crafting speed, and inserters will only insert items when the output is less that the maximum output on all crafting outputs:
The bug is that, if the speed modifier on the assembler changes after the fact (e.g. by placing a beacon, or adding a module), while the output limit gets increased, the waiting input inserters do not get woken up:
Note that the output inserter here is limited to full swings like this:
A newly placed inserter *will* still insert items, showing the inconsistency:
As soon as the output changes (either by other inserters filling the input or by manually changing anything) the previously stuck inserter will wake back up.
Annoyingly this issue can happen without adding new beacons/modules when the power drops low, reducing beacon speed modifier. Then the inserters might get stuck, and even when the power returns will not go back to running normally. (This is what happened to @Bamckup who originally encountered this issue)
My guess is that the change in assembler output limit does not wake up any waitlisted input inserters waiting on this slot changing. Ensuring this wakeup would fix this issue.
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Annoyingly this issue can happen without adding new beacons/modules when the power drops low, reducing beacon speed modifier. Then the inserters might get stuck, and even when the power returns will not go back to running normally. (This is what happened to @Bamckup who originally encountered this issue)
My guess is that the change in assembler output limit does not wake up any waitlisted input inserters waiting on this slot changing. Ensuring this wakeup would fix this issue.