Hi,
 I'm also owner of this type of GPU. What solved my problem was to lower the GPU's temperature (below 73'C, try more with additional fan if needed). Then it should be fine. If you have older batch of these cards (serial numer similar to 1348xxxx), try undervolting by Sapphire Trixx SW. With clocks around 1080 it should be stable at 1,081V, over 1100 rise voltage higher - 1.120-1.160V

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