Hi Martin,
thunbnails are generated on instagrams side and it looks like they clear out the cdn so the thumbnail_url becomes invalid.
If you want an all ways up to-date thumbnail to appear on your site i would recommend using the "embed_url" property to form query to instagrams oembed api.
const url = encodeURIComponent(data.embed_url)
const maxwidth = "500"
const token = "facebook-app-token"
fetch(`https://graph.facebook.com/v9.0/instagram_oembed?url=${url}&maxwidth=${maxwidth}&access_token=${token}&fields=thumbnail_url`)
Or is this an issue with the way things look in the editor?
Best,
Marc