I just checked on my laptop, android and PC browser, both on chrome and Firefox the issue happens on all of my devices. Basically I think what happens is that :
When you pick an avatar, everything is fine and the avatar is set on what it is supposed to be.
But after you click "Change profile", the field of avatar redirects itself to [Male] without any portrait picked, so the next time you click "Change Profile" the forum doesn't know which avatar you are picking so it goes back to the default one.
The issue for me goes through all of the portraits, from [Female] down to the [Special]
When you pick an avatar, everything is fine and the avatar is set on what it is supposed to be.
But after you click "Change profile", the field of avatar redirects itself to [Male] without any portrait picked, so the next time you click "Change Profile" the forum doesn't know which avatar you are picking so it goes back to the default one.
The issue for me goes through all of the portraits, from [Female] down to the [Special]