When current matrix HQ (!QtykxKocfZaZOUrTwp:matrix.org) was created, @aaron:raim.ist was incorrectly banned.

I later unbanned him (event_id $VzzqXFV0YpBgpHJhJz8GnurbSXuGAycgyDg5rLj5ksI).

However, the ban is now back in place. This appears to have happened when $FEqkc7QX6npeGWhKGGxMfFv6cl9TbQNkQsH3fWZpet0 arrived on 2019-12-09.

Initial investigation suggests that this is due to the fact that the unban is missing the ban from its auth_events.