If you throw ingredients for the metal press onto the input conveyor and then quit to menu (SP or MP) and then rejoin the world, then there's (as far as my best guess goes) a chance that the recipe/crafting process gets multiplied, meaning you get multiple times the output that you should receive.
The animations for these additional crafting processes appear to double upon each other and also lead to sound glitches/wrong press sounds playing. I assume the animation and sound issue goes away when the main problem is gone, but I'll still note it as an extra thing for now.
This happens for every mold as far as I can tell, but especially with the packing molds you can not only get extra recipe outputs but straight up infinitely dupe certain items, first and foremost metal ingots/gem stones. A stack of 64 ingots easily comes out as double to tripple the amount.