We managed to get this resolved.
The plugin EWWW Image Optimizer was intercepting file uploads in order to optimize images. Afterwards, it notifies W3 Cache to update the CDN, which fails because it's not able to access the W3 Cache object. The failure occurs in...
I just tried this, but I still get the same error: "http error" - No other information. - It happens with you try upload an image from within media library in Worpress