Hello, just started playing today, so I apologize if there's something I missed.

Is it intentional game balance that inserters will not load ore into the ultradense furnace while there is any metal in the output slot?
This is strikingly different behavior from the vanilla furnaces and not at all what I expected. It's actually quite aggravating to me.

I saw the other thread by Lutenar about "ultradense furnace weirdness" (https://mods.factorio.com/mod/Ultracube/discussion/659824ac727fe023bcb11132) and also noticed the same behavior. Is it possible these two bugs are linked? Maybe the ingredient slot got marked as a fuel ingredient somehow, so it gets consumed early? Maybe that slot category confuses the inserter logic for whether they should load the object or not?

Also I just noticed that I failed to categorize this thread as a bug thread, so please feel free to change that if you can, Seiken. I can't seem to find how I can do that, if it is available to me.

See the FAQ: https://mods.factorio.com/mod/Ultracube/faq
It is a bug in Factorio itself, and unfortunately is fixed for 2.0 but I can't do anything about it in the meantime. https://forums.factorio.com/viewtopic.php?f=7&t=101436

Thanks for linking the bug's forum post. Glad to hear how it's already patched for base 2.0.

Sorry for posting about something I should have checked the FAQ beforehand for.

Also this mod is a really fun idea and besides this bug I've been enjoying it. Thank you for making it!