This occurred on the US RustEZ Survival Server.
I had a 2 small furnaces running at a 3 split w/ sulfur and wood to make charcoal as well as burn down the sulfur, and 2 small furnaces running at a 4 split with just metal. I had just finished adding some new ore to the 4 split metal ore furnaces, and went to add some sulfur ore to the 3 split furnaces. When i added the new sulfur ore the 3 slots split in half reducing all 3 slots from ~1500 sulfur each slot (total of ~4500), down to ~750 each slot (total of ~2100). This happened because the splitter was still at a 4 split, and there was already wood, charcoal, and cooked sulfur in the 4, 5, and 6 slot.
That was a lot of sulfur to lose (over 2k) , considering i had just farmed it, and just started farming/building on that server. I left the furnaces burning sulfur as is, if you want to check it out.