Gumroad links don't work if the first image is a youtube video

I just updated my products to have a youtube video as cover. It broke the links in the thread: E-Cycles 2021 - 2x faster rendering with up to $100 off during winter sales!

Those 2 images should only be the miniature of the product like here:

Edit: I switched back to png on Gumroad, but would be awesome to have it work with videos.