Hello!
During editing long blog post (several days long edit session, with many save as draft events) I have noticed that some previously correct images got broken - displaying alternate text. They were visible on the edit session, replaced as text in "unpublished draft" view and replaced by "broken" icon when edited to reload them. Additionally, I have got one comment about broken images after publishing - which I cannot replicate (maybe cached image in my browser or intermittent error on retrieve)
One of images which I had to replace: