While we are having conversation about image, who have noticed earlier today the host was down? Who was here to put blame on? Web server or cloudflare? I do check the posts while I am on phone sometimes and I noticed this 500 error. 

In this case you are not giving image url to bbcode. This is link of the page which contain image but when you give the link of the image it's the image itself. What I understand, when image size is larger the host is taking time to return the byte, it's sometimes failing to load and sometimes it's loading. However it is working fine for small size images. There are nothing to do with link formatting or anything else.