I have a low priority factory (combat robotics, eh?) that occasionally runs low on input materials. In the direct-insertion steel smelting line (like the thumbnail), I've noticed that some of the steel-plate furnaces tend to run out of coal, even though their iron-plate furnace and burner partners have plenty of coal to share. I can't say for sure, but I think it only happens if the burner is busy refilling the iron-plate input stack at the moment the steel-plate furnace finishes its last morsel of fuel. In this case, after it satisfies the iron-plate demand, the shared burner inserter seems to not realize the furnace is now waiting on fuel.

The poor steel smelting furnace sits there unfulfilled in life and purpose, with the flashing fuel badge of shame, while the iron-plate furnace and burner-inserter gloat with their full fuel slots. What could a clever space engineer do to solve this predicament?

The simple fix would be to add a second inserter in between your iron and steel smelters, to give them twice the chance to fuel the steel smelter.

It's not an ideal fix, but troubleshooting the edge case is going to take some time.

Whew, I found the cause, fixed a tiny little typo, and sent a pull request. My global burner-inserter table was polluted with almost a thousand non-burner-inserter entities, and Burner Leech control was busy removing them one by one (about one every 8 seconds in my case), so some of my burners weren't getting their orders to pass the coal along. All is well now with the correction; my Lazy Burners are back to work!

playing with the Fantario mod which has an extended burner phase, I'll easily have 1000 or more inserters too (and all of them really are burner inserters), and thus they become "lazy" too. i mostly noticed such effects on my burner labs where LOTS of science bottles are forwarded all the time (chains "belt>inserter>lab>inserter>lab>etc") causing the inserters to use lots of fuel), and the burner inserters between them only fueled themselves a few times per minute.

if there is a bug in this mod that OkraDonkey has fixed, it would be nice to have that fix in the official mod too.

it also would be nice to have a shorter max period between checks (even when that might cause lower UPS), so that inserters never run out of fuel and/or never are "lazy" for 1 or 10 or more minutes (if there are 3600 or 36000 or more inserters); see my comment on "global.burner_index" at https://mods.factorio.com/mod/Burner-Leech/discussion/5d505b988b6d1d000dead917

The bug that okra fixed is already in the latest release.
It was an initialisation bug which caused the mod to add every burner entity to the global list and not just the inserters.