I think I have the same issue as you. It’s a pattern of squares flickering fast. I saw them when using max ISO but also on ISO 200 in almost black regions of the video. DJI told me to lower the ISO when I sent them video clips of the issue.
Somewhere I read that high sharpness setting causes this. I lowered my sharpness from +1 to -1 and saw a big improvement.
Try lower your sharpness, see if it helps.