Auto-generated password notice won't go away.

I cannot find another instance of someone experiencing this problem, but on my multisite network, sub-Administrator roles are seeing this notice:

Notice: You’re using the auto-generated password for your account. Would you like to change it?

That’s not actually true. I have changed the password for the accounts but this notice still displays.

Things I’ve tried:
Changing the password
Hitting “No thanks, do not remind me again”
Turning off all plugins
Using twentyfifteen
The function below

function remove_default_password_nag() {
  global $user_ID;
  delete_user_setting('default_password_nag', $user_ID);
  update_user_option($user_ID, 'default_password_nag', false, true);
}
add_action('admin_init', 'remove_default_password_nag');

This was happening before the auto-generated password and after it.

Where should I look next? wp-config? database?