yes, it's a test file in this case. I thought for a moment that it was coming from plugins, but I also tried disabling them. The crazy thing is that sometimes it works, but very rarely...

Ah yes I hadn't thought of making an abc, this will do for what I have to do, thx you.

Yes bacteria pushing others like bacteria billard, I have not tried with boids, I thought geometry node would be the best tool, apart from scripting. Thx for your answer.

I have reset first link with a full quality clip 1920*1080 for you see. I use 128 render sample and open image denoise. The strange thing is that it is only these objects that flickering and only when they are animated by translation.

Yes it's like this for simple solution but it's very long and not comfortable to anime this...