I’m getting this error too with images specifically. However, it’s not JUST from a PC, it’s from ANY computer. ALL of my contributors are having this problem and it’s a constant source of aggravation for reviewers and columnist trying to get their articles up in a timely manner.
Sometimes they work, sometimes they don’t. Sometimes I resize images and it’s fine, sometimes after I get an HTTP error, I just try 2-3 more times and it winds up working. There’s no real rhyme or reason to it.