I've an issue with blurry video thumbnails with a shopify theme (Flex from Out of the Sandbox). The image in the middle is a blurry video thumbnail, whereas the top and bottom one are regular sharp product images. Link to sample product.
I tested the content within different environments:
The video itself is sharp, which is visible when it's being streamed -> video is not the issue
The video thumbnail is sharp on another theme (Debut from Shopify) -> Shopify CDN is not the issue, must be the theme I am using
I also uploaded a cover jpeg within Shopify admin which didn't change anything.
I couldn't identify the problem by inspecting with the browser dev tools. Can somebody give me a hint how to fix this?