Well, I changed the composition it to premount all image sequences by 30 frames (my FPS) and it did not fix the issue.
#Black frames and flickering when rendering a lot of <Img> components
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Sometimes the flickering happens a few seconds after the image appears, so it doesn't seem related to asset loading. Although, since this is rendering in multiple tabs and chunks, I guess it can happen anywhere, not just on the first frame the image is mounted.