It's solved because AT&T knows what's causing it. Not that they'll tell you.
We are investigating this issue and are looking for more information to get down to the bottom of this. If you do experience this issue, please send us a private message. ... We thank you for your help and patience as we work on this issue.
So they dont know what's causing it, and they have not solved it.
Smiley Face, say it has been largely mitigated.
Ask for PMs for specific cases.
Making a widespread issue seem isolated as you implement a fix that affects 10M people.