If automatic backup fails, there should be a warning

[tgxworld (Alan Tan)]

Sure fixed in

Invite admins to automatic backups failure topic.

Note that inviting a group into a topic will now trigger the right notification as per

Inviting a group to a message does not trigger a notification mail

Fixed this in https://github.com/discourse/discourse/commit/2fdf9068eb6cdf640ad7628741588112932c7643