See attached video and you will see exactly the issue. It has been happening across several story maps I've created. Basically what is happening is when I open builder some images, not all, seem to resize into smaller thumbnails in my sidecar. I will get the notice that I have unpublished changes. When I select publish the image will appear normally in my sidecar. The video explains it a lot better than I can.
Thanks for reporting this Bryan. Is that story public, or do you have a public story where this is occurring, so we can investigate? We haven't seen this before, so I'm wondering if it's something to do with that particular image.
Here is one that is public. It is across multiple story maps that I have. You will not see the bug when viewing normally. It is once you enter builder/editor mode that the bug appears. I'm not sure how you are going to access that.
Regardless, if you can, you'll notice right away in the first sidecar image.