When using the Industrial Centrifuge, if there are inputs in both slots, a recipe will consume all of the input in the top slot first, ignoring the second slot until the first slot is already completely empty. This allows the player to complete recipes using far fewer inputs than needed.

For example, here's a recipe added with CraftTweaker for centrifuging redstone:

Here's the bug in action:

Here's another video with a different recipe:

You can clearly see the recipes completing and only using 1 of their recipe inputs, instead of the 48 or 4 necessary for the recipe.

EDIT: The bug works on the industrial blast furnace as well, confirming it's a bug common among machines with 2 input slots.

Here's a gif demonstrating it. (note that this uses the default 2 galena to silver+lead recipe, which means this bug affects for non-CraftTweak'd recipes as well)