Debian – dbus: [system] Failed to activate service ‘org.freedesktop.login1’: timed out

I keep getting the following error messages in the syslog of one of my servers:

# tail /var/log/syslog
Oct 29 13:48:40 myserver dbus[19617]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 13:48:40 myserver dbus[19617]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 13:49:05 myserver dbus[19617]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 13:49:05 myserver dbus[19617]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'

They seem to correlate to FTP Logins on the ProFTPd daemon:

# tail /var/log/proftpd/proftpd.log
2015-10-29 13:48:40,433 myserver proftpd[17872] myserver.example.com (remote.example.com[192.168.22.33]): USER switch: Login successful.
2015-10-29 13:48:40,460 myserver proftpd[17872] myserver.example.com (remote.example.com[192.168.22.33]): FTP session closed.
2015-10-29 13:48:40,664 myserver proftpd[17881] myserver.example.com (remote.example.com[192.168.22.33]): FTP session opened.
2015-10-29 13:49:05,687 myserver proftpd[17881] myserver.example.com (remote.example.com[192.168.22.33]): USER switch: Login successful.
2015-10-29 13:49:05,705 myserver proftpd[17881] myserver.example.com (remote.example.com[192.168.22.33]): FTP session closed.
2015-10-29 13:49:05,908 myserver proftpd[17915] myserver.example.com (remote.example.com[192.168.22.33]): FTP session opened.

The FTP logins themselves seem to work without problems for the user, though. I've got a couple of other servers also running ProFTPd but so far never got these errors.

They might be related to a recent upgrade from Debian 7 to Debian 8 though.

Any ideas what the message want to tell me or even what causes them?

I already tried restarting the dbus and proftpd daemons and even the server and made sure that the DBUS socket /var/run/dbus/system_bus_socket is existing but so far the messages keep coming.

EDIT:
The output of journalctl as requested in the comment:

root@myserver:/home/chammers# systemctl status -l dbus-org.freedesktop.login1.service
● systemd-logind.service - Login Service
   Loaded: loaded (/lib/systemd/system/systemd-logind.service; static)
   Active: active (running) since Tue 2015-10-27 13:23:32 CET; 1 weeks 0 days ago
     Docs: man:systemd-logind.service(8)
           man:logind.conf(5)
           http://www.freedesktop.org/wiki/Software/systemd/logind
           http://www.freedesktop.org/wiki/Software/systemd/multiseat
 Main PID: 467 (systemd-logind)
   Status: "Processing requests..."
   CGroup: /system.slice/systemd-logind.service
           └─467 /lib/systemd/systemd-logind

Oct 28 10:15:25 myserver systemd-logind[467]: New session c3308 of user switch.
Oct 28 10:15:25 myserver systemd-logind[467]: Removed session c3308.
Oct 28 10:15:25 myserver systemd-logind[467]: New session c3309 of user switch.
Oct 28 10:15:25 myserver systemd-logind[467]: Removed session c3309.
Oct 28 10:15:25 myserver systemd-logind[467]: New session c3310 of user switch.
Oct 28 10:15:25 myserver systemd-logind[467]: Removed session c3310.
Oct 28 10:15:25 myserver systemd-logind[467]: New session c3311 of user switch.
Oct 28 10:15:25 myserver systemd-logind[467]: Removed session c3311.
Oct 28 10:19:52 myserver systemd-logind[467]: New session 909 of user chammers.
Oct 28 10:27:11 myserver systemd-logind[467]: Failed to abandon session scope: Transport endpoint is not connected

And more journalctl output:

Nov 03 16:21:19 myserver dbus[19617]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Nov 03 16:21:19 myserver proftpd[23417]: pam_systemd(proftpd:session): Failed to create session: Activation of org.freedesktop.login1 timed out
Nov 03 16:21:19 myserver proftpd[23418]: pam_systemd(proftpd:session): Failed to create session: Activation of org.freedesktop.login1 timed out
Nov 03 16:21:19 myserver proftpd[23417]: pam_unix(proftpd:session): session closed for user switch
Nov 03 16:21:19 myserver proftpd[23418]: pam_unix(proftpd:session): session closed for user switch
Nov 03 16:21:19 myserver proftpd[23420]: pam_unix(proftpd:session): session opened for user switch by (uid=0)
Nov 03 16:21:19 myserver dbus[19617]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Nov 03 16:21:19 myserver proftpd[23421]: pam_unix(proftpd:session): session opened for user switch by (uid=0)