Hair flickers in the render

Hair shimmers in render.
In the video, this is clearly visible, I would like to leave the video here, but I cannot because of the conditions of the site. I will try to leave different photos and I hope everything will be clear from them.

But first to clarify:
I am using Blender 2.9.
In Blender 2.8 I faced this problem 20%, but in Blender 2.9 it became 100% of the time.
Using the same hair and render settings, I had flickers and sometimes none. I have absolutely no control over this process!

Here I will leave everything that will help you and thank you very much for your help! Otherwise I am desperate and cannot work any longer …