In Mekanism 1.5.2, the version that modpacks such as Voltz uses, there is a bug that lets you duplicate robits. You put a robit down, put something in it's inventory, then make it go through a lit nether portal. As soon as it touches the portal, it will drop 2 of itself, with the inventory duplicated. This is an issue since many modpacks still use 1.5.2, and im sure that less bugs is always good

This was fixed with the release of v6.