Miner is stable, your hardware isn't. I have isolated the culprit card in my restarting rig and managed to make it run stable with v9. Now It hashes a little lower then the rest of my cards and still higher than v8.
Sure you have to look into what's happening in your rig, it doesn't work stable out of the box like v8 if you have weak components. Increased hashrate comes at a cost.