All ore is *supposed* to get "frozen" in the furnace when you try to input it for smelting - The "actor" is supposed to get locked
Currently only "one" actor is getting locked, resulting in some misc bugs/exploits with the other ore and smelting - but the one that is locked, is not a bug.
The "not enough fuel" is an entirely different issue altogether.
Not enough fuel can be caused by various thing
1) other stations/physics hit boxes could be in the way of one or more of the detectors - From my observation I ASSUME... there is a "Fuel detector" an "ignition detector" and an "output detector".
The Fuel detector is tied to the meter that visibly displays how much fuel is present - you can exceed this, though the meter will just remain in red for the majority of that. - The "ignition" detector IMO is what causes the majority of "Not enough fuel" as this would be the detector that targets a piece of coal or wood and starts burning it for heating and smelting. - If this detector fails in some way, it won't burn wood, won't tell there's wood to burn, and thus, nothing will occur. - Output Detector will allow heat to work, but prevent smelting to work, if only the output detector is blocked (near the casting tray) - when only this happens, its usually simple enough to fix.
2) a second possible way is both fake fuel and fake readout - Not much I can really say about this one, sometimes it just seems like fuel disappears or that the readout is empty with fuel in it. - saving and reloading will usually eliminate this - as its usually either the fuel is actually burnt already, and for whatever reason their visuals remained, or perhaps the fuel detector had something happen, I don't know.
3) This way is more user error, and can be avoided by not trying to smelt more than a small small number at a time - and that's by putting too much ore in, and requesting too much output - not only would it take forever to heat up for each additional ore chosen, but the thing only reads so much fuel at a time, right? - even if it can have more plaed inside that it knows what to do with.