Color Banding and Gradient Flicker While Editing Vertical Webtoon Panels in After Effects

I’m currently working in a private company as a video editor, and one of our clients recently approached us with a project for their website https://newtoki.com.co/ since this is a webtoon platform, 

that edit involves long vertical panels with smooth scrolling and gradient backgrounds. The issue I’m facing is unusual: gradients that look perfectly fine in the After Effects preview show heavy banding and even flicker once exported. This happens in both H.264 and ProRes, and it’s especially noticeable in soft sky tones or dark-to-light transitions.

I’ve tried higher bitrates, switching to 16/32-bit color, and even exporting image sequences, but the problem still appears. What makes it trickier is that not all panels are affected some render cleanly, while others with the same settings show the banding. Since webtoon edits rely heavily on large gradient areas, this artifact really breaks the flow and makes the final output look unpolished.

Has anyone else run into this kind of gradient banding and flicker in vertical scroll animations? Any reliable workaround beyond just adding noise or dithering would be a huge help.