Source ID 340 was not found when attempting to remove it

[Chris]

The entire notation in my syslog is:

Sep 17 09:01:06 localhost gnome-session[3616]: (gnome-shell:3665):
GLib-CRITICAL **: Source ID 340 was not found when attempting to remove
it
Sep 17 09:06:45 localhost gnome-session[3616]: (gnome-shell:3665):
GLib-CRITICAL **: Source ID 4353 was not found when attempting to
remove it
Sep 17 09:09:41 localhost gnome-session[3616]: (gnome-shell:3665):
GLib-CRITICAL **: Source ID 5780 was not found when attempting to
remove it

As you can see this happens about every 3mins or so and the source ID
increases each time. I filed a bug with Gnome however since I'm running
3.18.5:

gnome-shell:
  Installed: 3.18.5-0ubuntu0.3
  Candidate: 3.18.5-0ubuntu0.3
  Version table:
 *** 3.18.5-0ubuntu0.3 500
        500 http://us.archive.ubuntu.com/ubuntu xenial-updates/universe 
amd64 Packages
        100 /var/lib/dpkg/status

which is outdated and unsupported I had the bug report voided. I can't
see any problems with the system operation it's just an annoying
notation since I can't figure out what's causing it. Is there any way
to try and track this down? I'm running

lsb_release -rd
Description:	Ubuntu 16.04.3 LTS
Release:	16.04

At one time I was using Gnome Shell 3.20 however when the PPA shut down
I regressed back to 3.18.5.

Chris

-- 
Chris
KeyID 0xE372A7DA98E6705C
31.11972; -97.90167 (Elev. 1092 ft)
09:03:45 up 8 days, 16:32, 2 users, load average: 1.04, 3.47, 2.30
Description:	Ubuntu 16.04.3 LTS, kernel 4.10.0-33-generic