I have the same problem now with 10 Iron Ores in the cart at the Furnace. You’re not alone. Would be nice to see a fix that doesn’t involve sending the wolf out and back to the furnace again.
I just came here to report this, too. Six iron ores in the mining cart and it won’t smelt an iron bar. I really don’t want to waste resources going back to mine to get it to reset, but if it’s the same bug that existed in beta and early access, I won’t have a choice... It’s consistent across different browsers as well as mobile!
edit: when I dropped one ore, the other five smelted. Definitely not a perfect solution, but much better than heading out again. Hopefully that saves someone a trip :)
I'm glad this thread exists, because it's nice to know I can drop one of my extra copper ores to smelt the 10 iron ores I have ready. This isn't the first time I've had this exact issue, but it is the first time I dropped an ore and my miner started smelting again. :)