I'm having a problem with embed displays. Not with every embed, but with quite a few, in multiple courses.
1. Embed initially looks good with a nice preview image.
2. Some time later, after time passes and courses are closed and opened, the preview image no longer looks good even though the metadata is still pulling correctly and the link is not broken. See, for example, the attached image. The link (https://rscj.org/key-figures-in-our-history) still works fine, but the preview is bad. This happens in Edit mode and Preview mode.
3. Generally, if I re-embed, Rise will pull a good preview image again. This is not always permanent, and sometimes it's not the same image that was originally pulled.