[Samba] Are secure DNS updates truly working?

[George]

Hi team,

I recently upgrade some servers from v4.3.5 (affected by
https://bugzilla.samba.org/show_bug.cgi?id=11520 ) to v4.5.8 (default in
Debian Stretch) and was expecting secure DNS updates to be working again,
but they are not.

My logs show the same issues reported on bug 11520:

[2017/08/29 15:21:01.990467,  2]
../source4/dns_server/dns_update.c:773(dns_server_process_update)
  Got a dns update request.
[2017/08/29 15:21:01.990841,  2]
../source4/dns_server/dns_update.c:730(dns_update_allowed)
  Update not allowed for unsigned packet.
[2017/08/29 15:21:02.001791,  1]
../source4/dns_server/dns_query.c:880(handle_tkey)
  Tkey handshake completed

DNS records are not updated by Win7 clients and a Wireshark capture shows
Samba returns "Refused" to the request (I'm using Samba internal DNS).
Setting "allow dns updates = nonsecure" works fine, as before.

Can anyone confirm that this was indeed fixed? What else could be the
reason for the failures?

Thanks,

George