Blotchiness and banding in gradients?

I am creating a banner ad in Adobe Animate. There are several gradients in it theat client is very fond of. They look good when i scrub the timeline in Animate, but when I watch the preview movie, there is banding and blotches in the gradients. I have seen other banner ads with gradients that look good, but I'm nervous that this blotchiness will show when it's on the web. Which preview should I trust? Are gradients in Animate a bad idea? Is there a way to safely use gradients in Animate?