I just bought the GL-AR750. It will not allow me to use a special character (# for example), and still accept it in the root password area for the Admin Section.
I have gone into the Admin Section to manually change it as well, it will save it, but then the old admin password is required for the router login.
Obviously some bug exists.
I have done a factory reset and I am using the latest firmware 3.027, but no go.