That image originates from another server, when the URL is provided (as part of the post), it's fetched to a content server, and loaded through a proxy service (perks: resolve non-SSL endpoints via SSL and provide tracking).
The entire URL is being passed in as a parameter, and it uses local caching to serve it up:
Code:
https://forums.macrumors.com/proxy.php?image=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F9%2F91%2FAdium.png&hash=6b7d292a0413e216e1e64341bffda985
The original image file is sitting here (extracted from the image proxy param):
Code:
https://upload.wikimedia.org/wikipedia/commons/9/91/Adium.png
You can apparently toggle back to a direct image link (so it would use the above) vs. using the proxy and locally cached version (though losing the benefits I mentioned above).
Anyway, I've got just the image URL from here (i.e., proxy.php?<imageparams>) open in two different tabs, same browser, one is broken (aka, "red X"), the other is loading, I see that the headers are different. One is allowing a long duration to read the cached version, the other it first requiring a lookup to see if the original has been changed (that's via the cache-control and ETag headers). The tab that's "no-cache" is breaking, over and over, it's trying to resolve the resource and can't, while the other tab (and other browsers) are loading from the cache-server successfully.
Check into your cache control, expire time, anything about updates/patches to resolve caching/cache-control/header, etc., all the content/CDN stuff, assuming that's part of the hosting service and provided by Cloudflare.