I recently upgraded from Mekanism v7 to v8. I have one large Dynamic Tank storing large amounts of Liquid XP (from OpenBlocks), and another storing the brine from my Salination Plant. However, at seemingly random intervals, the Brine Tank's inventory disappears and is replaced with more Liquid XP. (I've seen this happen with other pairs of tanks, but this is the most persistent problem). Neither tank is anywhere near the other, and in fact they're located in different worlds. Sometimes pumping the liquid out of the second tank decreases the inventory of the first tank, sometimes it doesn't.

My best guess is that the game gets confused about which tank multiblock to associate with which inventory.

This bug is fixed in the very latest version of Mekanism, the system of multiblock caches was refactored to avoid problems like this.