At least since 1.6.0rc1, Mastodon has been reporting an error when users submit a follow request to users whose accounts are locked (i.e. require authorization before following). The error is:

422 Validation failed: Username has already been taken

It is often accompanied by a 500 error.

However, the follow request goes through! The target user can see and approve or reject the follow request, but the following user must refresh the Mastodon browser window in order to see the user on their timeline.

I noted this issue when researching this, but it may not be the same problem and predates 1.6.0rc1, which is when I first noticed this issue.

• I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• This bug happens on a tagged release and not on master (If you're a user, don't worry about this).