When furnaces/smoker/blast furnaces are unloaded and reloaded, its method with CookTime and CookTimeTotal is broken. It happens when datapack recipe defines cooktime larger than 32768, because it stores it as Cooktime as int16_t, which is - signed cooktime. Then furnace type block entities would not cook anything, but consumes fuel, adds cooktime, infinitely. Progress bar would be seemed like 'reversing', because it renders by referring abs(cooktime-cooktimetotal) / cooktimeTotal.  

We could easily check if the error occured by getting block nbt data, checking for cooktime > cooktimetotal.