Map Bosses That Drop Absolutely Nothing

This keeps happening, there's two areas where the boss dies and I don't even get a replacement weystone, not a single item. That's so wrong, it's gotta be a bug. I have never seen that before in this game. It just happened in Sulphuric Caverns. I'm only posting because it actually really just f'd up my progress because I was advancing through and won a glorious boss battle and I was and really counting on that weystone (I know they weren't always 100%). But I can tell there's a bug and that sets me back a few tiers back to tier 2...
Bad enough I lose weystones to disconnecting, and bosses are bugged.

Edit: I'm noticing that it happens on the dual boss fights.