Thank you.
Using my pc I to view the list of gpx tracks on my gps I found that TRACK was not on the list, even though TRACK appeared on my gps itself.
However, I did take note of the tracks before and after TRACK on my Garmin view of my gpx files which gave me an idea of where TRACK might be on my gps. I then went again into my pc and opened my list of gpx tracks on my gpx files list. Track was not visible on the list, so I deleted the two tracks which I had determined were either side of TRACK. I then disconnected my gps and restarted it. I'm happy to report that TRACK was now gone from my GPSmap64s.
Because I had previously saved externally the two tracks I suspected to be on either side of TRACKS on my gps I was able to return them to my gps where they were not hindered by the presence of the file 'Track'.
So far all is well.