Uploading images can be very slow. It is a background process that continues even if you close the window with the progress bar ( but is interrupted by a reload). Roll20 connects to different internet services, images are uploaded to AWS S3. The game data is synchronized via Google Firebase. The connection lost messages shows that the browser lost the connection to firebase. Reloading does normally not help ( as the message in the red box indicates) as the browser is trying reconnect constantly. Images are also downloaded from AWS S3, when upload is slow the same goes for downloads. This is an explanation for elements=images not loading. So when uploading images its best to wait till the end. Do not F5, ignore the connection lost red box. If you upload large jpgs, be aware that these are converted to png before upload and that each is uploaded in increasing detail (thumb,min, medium, max, original). With a large jpg (3500x3500, 8 MB), the original can become 40MB. A casual drop of a few of those can take hours to finish. Especially when netflix and primevideo max out the interconnect between you ISP and AWS.
