2017 iMac 4.2 GHz Quad-Core Intel Core i7 running OSX 11.4 Big Sur. It happens especially when using graphics or video programs. I tried everything. Please give me some advice. reset NVRAM reset SMC new fresh installation I still couldn't find a solution. I connected the second monitor, and the flickering continues on the second screen, too. (both have) I used the screen recording, and I saw, in the recording, everything seems fine; there is no flickering in the screen recording, but in real-time, there was a lot of flickering. So, the recording shows nothing. I guess it is not a screen hardware problem (the second monitor has also flickering when I connected) What do you think? Is it about the GPU, graphic card, or processor?