Easing or blowing sheet is effectively powering up the kite. If you are in a round down, you are probably by the lee, right? The apparent wind is "telling" the spinnaker that it is on the other gybe. When you ease sheet you are increasing the power in the spinnaker that is trying to pull you over to windward. Same with easing the vang, as others have stated. Try sailing a Laser DDW in breeze with the vang off. Look at the leech wrapping around forward, presenting all that area and leverage to the breeze that wants to push the mast to weather. When the boat starts oscillating, pop the guy forward 2-4 feet, depending on boat size. When things settle down (almost immediately if anyone has half a clue) square back and bear off again. Repeat as necessary. If you are oscillating beyond recovery, it is always better to bail high side than low. Never blow the afterguy (brace.) Ease it before easing pole downhaul. That may keep the pole off the sidestays. Twings down choke the kite well, effectively depowering it, but remember to free things up in the lulls.

We make damn sure there is not a stopper in the spin hal.