if you used a different connection and still experienced the same problem, then it sounds like your machine(s) are the source of the problem.
back in the day on older Windows machines, i noticed that i would often have issues with uploading on machines with relatively small amounts of RAM (4GB or less). the problem typically manifested itself more as sudden unexpected freezing of the page, requiring reloading, but i wonder if on MacOS, inadequate memory could manifest as the problem described here in this thread?
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your issue (images not loading on the observation detail screen) is different from what most of the people on this thread are reporting (problems uploading images on the upload screen).
you can try restarting your gateway, and if that doesn’t help, you should probably call your ISP to see if there’s something they can do to fix things.