Whenever smelting large numbers of objects (such as a stack of iron ore or the like) I have found that typically one or two items remain unsmelted despite inputting the correct amount of coal. This could possibly be caused by server-side lag.
To this end, there is a possibility it may only be reproducible on minecraft servers with server-side >50 ms lag.
Comments 8
I used 8 coal to smelt 64 iron ore (in two different furnaces) - in one furnace, only 63 items were smelted. In the other, only 62, but the coal entirely consumed as if it had smelted 64.
Possibly. However in other occasions when every chunk was loaded he whole time they still displayed issues.
Furthermore, both furnaces are on the same chunk, so I doubt that unloading the chunk would cause them to lag differently.
I can't think of a reason why this bug should happen. Can you make sure you did not made a mistake by accident?
I just verified it. I put 8 coal into a furnace to smelt 64 cobblestone blocks and watched for the entire time. The coal burned at a rate of about ~102% +/- 0.5% that of the stone. I was present and had the furnace open the entire time. I could send you the server IP if you would like to personally reproduce it.
Is this still an issue in the most recent versions (currently that is 1.12.2, or the latest 1.13 development snapshot 18w07c) of Minecraft?
Can you please describe the exactly which and how much fuel and items to smelt you used?