let me do the maths for u
u inserted 156 gold ore (every 3 makes 1 bar) so this resulted in 52 gold bars.(156/3) this procedure ended
and started melting bars (every bar makes 5 coins) , so this resulted in 260 coins. (52*5) this procedure ended
and started melting coins back to bars (every 30 coins make 1 bar) so this resulted in 8 bars (260/30) this procedure ended
and started recrafting the 8 bars into coins (each for 5 coins) so this resulted into 43 coins (8 aprox *5) . this procedure ended
and then the 43 coins re melted into the equal bars they could do… so 30 coins became 1 bar and u r left with 13 coins and 1 bar…guess what the last bar turned into… yup coins… so u ended up in 13 coins which was the step above and 7 more (if u do the exact maths as i have them u will see that u end up in 7,222 coins ) which means 13+7 = 20 and this is what u see… as all the above r calculated instanty…
that is why u end with 20 coins… the furnace will not stop untill the quantity of the bars or coins cannot be remelted… hope it helps u to understand
edit: i just re read the post… will try to duplicate as ur issue is not the recrafting thingie… but the conversion rate
(sry about the above! i brainfarted it seems)
edit: i just tried to melt gold ore and it melts normally
u reproduce the bug all the times? used coal and daya as smelter…