What are you talking about? Blizzard has not suggested doing anything with the UI and certainly has not suggested installing a different version of Battlenet.
The official information is at the top of the launcher and in the TS thread with Blue posts.
Can you please link to anything, anywhere, documenting Blizzard saying to “rest” (reset?) the UI or reinstall Bnet?
For the record, the issues seem to be resolving for most folks and they can log in. Those that can’t can post on the TS thread.
EDIT:
I see where you misunderstood the info. We are on step one - widespread issue impacting all chars and announced on the launcher, CS Twitter, and forums. This is NOT an issue iwth a single char that someone would reset a UI For. Further nothing here says to install an older version of Bnet. https://us.battle.net/support/en/article/10660
If you’re receiving this error on all characters, check the Realm Status page and BlizzardCS Twitter for widespread issues.
If this error happens on only one character, you can resolve it by moving the character. If the issue persists, reset your user interface and try again.