Changing the 'birth' date of a Twitter account to anything less than 13 years old results in the account be immediately locked without warning and without a mechanism to reset. This is obviously an age consent control but the undo has disappeared.

Lots of posts complaining about this to the Twitter support account. Especially problematic for a brand or organization account younger than 13 years. Ironically @twittersupport was born in March 2021, so they seem to have slipped themselves through the net!