I’m actually starting to see this problem now even on newer versions of Gitlab. It started when I upgraded from 8.0.3 to 8.0.4, continued to happen when I upgraded to 8.0.5, and is still happening even after I upgraded to 8.1.0. I get the broken link image and when I try to manually go to the image URL:
It comes back with an empty page.
Edit: Ok, this is weird. When I browse to that URL in a browser, I get a blank page. If I fetch it with curl, I get a 404 error. However if I paste it into this message window
It shows a valid graphic.