It has been a little while since I posted my question on the
smartmontools support forum.
Thanks for the primary answer I got from Robert S.
To my own disgrace, I must now admit that I have been wrong by saying
that the device about which I got this health warning did not exist on
my system. It DOES exist!!
However, a complete health scan was never performed before, as I
discovered. I then let it run once and I haven't seen a warning since then.
Therefore, I suppose that this post can be closed. Should the messages
about this drive appear again, I can post a new question if necessary.
Thanks anyway for your attention.
Kees van der Wiel