Sometimes folder and file permissions in DM server accounts get reset in strange ways by how you are copying your files around and putting them on the server (for example, emailing things to yourself, downloading from Dropbox, etc.)
These and other actions may reset file or folder permissions in ways that don't become apparent until your files and/or folders are submitted to the server and you try to view your project through the web (using the URL, and/or using the link on the Student Work page).
The permissions problems may come to your attention when you view your project through the web and some files (images, for example) won't load even though you have checked many times that you uploaded all the A1/A2 files and linked/loaded those files on your pages correctly. Or, you may get a "Forbidden" message when you try to view your project through the web.
Another permissions problem becomes apparent to me (but not to you unless you get an email from me) when I try to copy your project from the server so that I have a backup version on my laptop to mark. Sometimes permissions are set so that they won't allow me to copy anything for marking, even though the files/folders are viewable as normal through the web.
IF the setting is not allowing you to change it to Read Only: