To clarify, the user linked to several files with a naming convention like "http://juotpics.com/s/simpsonscredits 11.jpg" (note the spaces in the file name). When embedding the image in the editor the image is viewable and, after saving the post and then hitting 'edit' again the image is viewable, but trying to view the saved image results in no image.
I tried the same test here (https://xenforo.com/community/threads/proxy-image-test.90194/) and, as shown in post #2, I got the same results. If I manually change the spaces to %20 then it works as expected.
Something to do with the image proxy code or something I can do on my VPS to take into account?