I am playing AoF 2 version 3.0.0 in case there is a mod interaction causing this.

when shift clicking the output of a crafting station sometimes I will get a second output (eg put in the resources for exactly one iron pickaxe and occasionally receive two) the second output will disappear if clicked or held.

I haven't found a way to consistently cause it, but it does happen occasionally when crafting non-stacking items and once even output a different item (crafting an iron pick yielded an iron pick and a "ghost" iron hoe).