I ran into same problem with units that had been removed. try
sudo systemctl reset-failed
from
http://www.freedesktop.org/software/systemd/man/systemctl.html
"reset-failed [PATTERN...]
Reset the "failed" state of the specified units, or if no unit name is
passed, reset the state of all units. When a unit fails in some way
(i.e. process exiting with non-zero error code, terminating abnormally
or timing out), it will automatically enter the "failed" state and its
exit code and status is recorded for introspection by the
administrator until the service is restarted or reset with this
command."
--
Paul Morgan