so im not 100% sure this is because of this mod, but i suspect its either the culprit or at least a big contributor

when barreling fluids ie light oil, then unbarrel you get a gain of fluid..
using any quality barrel other then common, you will get a net gain in fluids,
a standard barrel usually takes 50 light oil, but with a legendary barrel it will output 90 light oil.
so setting up a simple loop barrel and unbarrel, you will end up with a net gain

not sure now it might be done by code directly, but i would suggest a method to close the loophole and exploit

barreling required fluids = same as unbarreling fluids
so both scale on quality