This solution worked for me. I used nano instead of vi, which IMO is more user-friendly:
Drop to terminal and enter
sudo nano /lib/systemd/system/open-vm-tools.service
In the document that opens, add under [Unit] the following line:
Save, then reboot. Thank you j2clerck!!
Yes, this works!
Definitely easier with nano, indeed...
BTW, Ubuntu 18.04.1 LTS now has the same problem, after the latest updates, thus requiring the same workaround.