Okay, quick update - I have seemingly narrowed this down to requests from my server to Imgur being blocked which is why old images are failing. Images linked via HTTPS should work fine but HTTP images are being run through a proxy that reaches out to the server to confirm the file is valid and actually an image. These requests are failing which is why the image is not loading. I have submitted a ticket with Imgur support but for now, older images are going to stay broken. If you want to decode the URL, you can still get to the original - just right click the broken image, choose open in new tab, and the image URL is the text between src= and &hash.
For instance, the URL in your image is http%3A%2F%2Fi.imgur.com%2FJoU63RI.png and you can paste that into any online URL decoder to get a usable URL or do it manually:
%3A = :
%2F = /
Depending on the source URL, there might be other characters you need to decode at which point it's probably much quicker to just use a website.
For instance, the URL in your image is http%3A%2F%2Fi.imgur.com%2FJoU63RI.png and you can paste that into any online URL decoder to get a usable URL or do it manually:
%3A = :
%2F = /
Depending on the source URL, there might be other characters you need to decode at which point it's probably much quicker to just use a website.