Perfomance drops / not a heat problem

Hi all,

I find that the speed of my GTX 1080 graphics card in connection with WPA2 drops from about 420 kH/s to approx. 31,000 H/s during approx. 2 minutes.

I have checked that I have the latest driver and that there is no dust that prevents cooling.

Constant temp. readings: Dev.#1.....: Temp: 57c Fan: 33% Util: 92% Core:1936MHz Mem:4608MHz Bus:16
Watchdog: Temperature abort trigger set to 80c
Watchdog: Temperature retain trigger set to 75c
I have previously not experienced a decline in speed.

Do you have any suggestions for what I can do?

Thanks in advance.
gg