It seems that with some profiles the Gravatar image is broken. I am not sure if this is an issue with SE or Gravatar, or both, so posting here.
Profile image on SO:
Image on Gravatar:
Switching to the MSE profile of the user, the image is working (but has a different hash).
Is this a bug on the SE side? Can anything be done to make Gravatar fix this?
It happened to me again two times today. The last user profile was this one. Calling the service two or three times fixes the issue.