I have encountered a bug where if you leave items in any furnace from the Iron Furnace mod then leave the dimension or logout then the contents of the furnace will disappear. I don't know why this happens but I have lost so many items trying due to this and it has become increasingly annoying since I can't leave things to smelt automatically without risk of losing it all.

I have had this issue as well. Additionally, i have seen other blocks clear their items/data:
Wireless Heater (Iron Furnaces)
Simulation Chamber (Hostile neural networks)
Experience Crystal (Utilitix)
Possibly Windmill Bearing (Create) (Need to keep resetting the bearing. Hard to tell with create so it could be a separate bug)
Basic Wireless Player Charger (wirelesschargers)

I believe this is fixed here, but the 3.1.1 version of Iron Furnaces didn't make it into the latest ATM7 update.

I'm not experienced enough to read the changed that was linked. But my experience with a Golden Furnace from (Iron Furnaces) currently is that it's state isn't saved / loading properly. All settings and inventory is empty when I return to it.

I am using ATM7 Version 7.0.2.13 and manually updated IRON FURNACES version to 3.1.2 and this has been corrected, or at least confirmed fixed the issue on Single Player Worlds

I have been playing around with it and yep updating iron furnaces works, also updated Utilitix to 0.3.2 which fixed the experience crystal. Tried updating hostile neural networks, to 3.0.4 but got a crash on startup. I'm going to guess something has changed in an API and we might just need to wait for individual mods to be updated to fix it.

duplicate of #117