Often, when attaching a tall image, it gets a fixed width on the thumbnail, causing the image to flow all the way down into the comments section. When this happens, it can be impossible to delete the image using the trash can icon (you have to Manage Attachments to delete). It is random when it decides to do this. Sometimes, we'll try to attach the same file again and it will attach with the default-sized thumbnail. I've attached an example of this happening in our sub-task.