Speed drops
Comrades, I welcome You.

I am interested in this question: to calculate the WPA2 hash (code 2500), I use an NVIDIA Quadro M6000 video card. When you start the hashcat program, the hash rate per second starts at 290 Kh/s, 2 minutes pass, and the speed immediately drops to 280 Kh / s. Before that, I get a message that the operating temperature has reached 90 degrees. I measured the temperature of the video card and it is stable at 83 degrees, not higher or lower. But the main question is that at a working temperature of 83 degrees, the hash calculation speed still falls, just after half an hour, the speed is already 260 Kh/s. Please tell me who has faced such a problem, what should be done, why is the speed falling? Thanks.
Speed variantions over cracking is quite normal in the range you are reporting. It depends mostly on the type of attack, the number of hashes you are cracking, number of masks etc.
My GPU does the exact same scenario, I've never considered it an issue just that I'm using my PC while I am cracking wpa2 so I expect there to be a variance in my speeds.

Most times my 1070 will start at 360Kh/s and reduce to around 320Kh/s after a short period. It usually maintains around 320-340 but I've seen it as low as 290 while using my PC normally. Also choosing the right workload profile could help in maintaining the speed. Using -w 4 would most likely put your PC at a stand still where as -w 3 you can still manage to operate your PC normally.