Take a look at the screenshot of the spreadsheet in the first post. Notice that some of those image rows start with https://www.appsheet.com/remote/ with an encoded URL coming after that.
The purpose of /remote is to resize images. So if someone adds an image to their app with a full URL to an external location, we will send that image through the resizer so that the app loads faster. That behavior happens automatically within AppSheet. In this case though the URL already has remote in it so the image is actually being passed through remote twice which I guess could cause a problem.
The reason that there have been problems with this recently is that previously we couldn’t handle https links in the remote resizer. Now we can so there was a change a few days ago that caused more links that previously would not have gone through the resizer to start using it.