I'm aware similar issues have already been reported, but I'm able to consistently reproduce another strange aspect of the bug on step 5:
- Edit my profile on any non-beta Stack Exchange site
- Click Save and copy changes to all public communities
- My profile on all other sites, including the meta site of the main profile that was edited, now use the Identicon image
- Navigate to my main profile on another site, click Change picture, and select "Gravatar"
- Click Save changes just for this community
- My profile on the respective meta site still uses the Identicon image
- Navigate to the meta site, and simply click Ask Question
- My profile on the meta site now uses the Gravatar image?!
In the meantime, I've opted to upload my profile image manually rather than going through gravatar. That appears to apply the change to all my networks without issues, as far as I can tell.
I thought that reporting these bizarre reproducible steps might help narrow down the cause of the bug.