Another ghastly fluid issue comes from the milk: while getting milk from the backpack's ability, the tooltip says both tanks are filling to a bucket worth of milk, while the right one is actually empty. At the end of the process, the error will not leave: the tooltip will still say both tanks have 1000mB of milk. The problem persisted until I filled the right tank with water. I am supposing this is a bug from the backpack's ability; today I'll make a melon backpack and let you know if the bug lays in that one as well.

NOTE: I didn't try any other backpack than the cow one, as of the time of this writing.

Another sync issue related to the cow ability.
That code gives me headache. -.-