I’m having a similar problem. When I drag and drop thumbnails into the wysiwyg editor, it fails to add the directory name that my WordPress install resides in. So, instead of https://www.hostname.com/wordpressdirectory/wp-content/uploads…, it changes the url to merely https://www.hostname.com/wp-content/uploads, causing a broken image. However, if I right click on the thumbnail I want to add and select “Send to Editor” from the menu that pops up, it works fine.
