Description of the issue:

Should be easy to replicate: Items like leather armor or bows that have no recycle recipe can not be manually put into the furnace, whereas itemducts/pipes/hoppers/conduits will stuff everything in with no regards to available recipes. Once in, items without any recipe can't be pulled out, effectively clogging it.

Versions & Modlist

Minecraft: 1.12.2
Immersive Engineering: 0.12.88
Forge: 14.23.5.2781
Enigmatica 2 Expert: 1.56

I haven't tried to replicate the issue in a clean instance yet, but I will as soon as I can.