Hey there,

I am really sorry for the delay of this reply as it is a weekend for us here.

I've tried to upload avatar from your admin account, it seems work fine, you can refer on my attached screenshot below.

By the way, when you press `save` button, it actually save all other details e.g. site details, profile URL, location and etc, so I believe system detected your custom profile URL already have other user used it, perhaps you can double check on this `Profile URL` section and see how it goes? (Refer on my second attached screenshot).