Opening a file on the desktop shows dbus error

I guess this is more like a call for help than a bug report. Sometimes when trying to open a file on the desktop using 4.16.x I see this:

This happens in an unpredictable way. Also, once you boot and you have the error it will always show in this session, until you reboot and wait to be lucky or not...

What is consistent is that the error only occurs when accessing files directly from the desktop (accessing it from the desktop folder using thunar works nice) and if you open with double click or enter -- right clicking and selecting open with 'mousepad' never triggers the error. Also, it doesn't matter which file extension / application associated. Finally, even when we have the error message, the file opens anyway.

I understand that this issue might have been fixed in 4.18.x, but any help on where I can find the code responsible for this error or a related ticket would be very helpful.

Thanks!