Imagine this:
In version 1.1.xxx this electric furnace melted 12 ores in 144 ticks. It worked for sure. I do not know what you changed, but now, this furnace melts 12 ores in 160 ticks. Maybe it is ok or maybe no, it does not matter. The problem that I complain: sometimes this furnace will only melt 11 irons in 160 ticks. This happens every 5-7 times. There may be a rounding error in the Factorio's calculus.
It may be related to this: 72618
I checked it without bottleneck mod as well.
+489% speed, possible round error in calculation
Re: +489% speed, possible round error in calculation
From 1.1 to 2.0 Beacon mechanics have changed slightly, which affects Machine Speeds.
Factorio rounds Displayed numbers; the crafting speed of “11.78” divided by the Recipe time of 3.2 Seconds equals 3.68125 Inputs per second… This doesn’t work out to an exact number of Ticks, so you get small “differences” between the Infoboxes and the Production Statistics….
Much like the proverbial tree in an empty forest, if the machine is working and not Input Starved or Output Full, is it broken?
Factorio rounds Displayed numbers; the crafting speed of “11.78” divided by the Recipe time of 3.2 Seconds equals 3.68125 Inputs per second… This doesn’t work out to an exact number of Ticks, so you get small “differences” between the Infoboxes and the Production Statistics….
Much like the proverbial tree in an empty forest, if the machine is working and not Input Starved or Output Full, is it broken?

Re: +489% speed, possible round error in calculation
did not waited other response