The only way I can get to a proper avatar screen to change is by doing the following.
On the home screen click on your avatar on the right. Brings up the dialog box. You then click the avatar there. This brings you to your profile page as the public views it I belive. ONly from here you can then click the Avatar in the top left and bring up the dialog box and bring up the Avatar Editor.
Going to your own profile in the backend for your user and attempting the avatar change does not work, like showed in the previous post I just made.