baabel
14
The engine is updated to version 110518-1 and the current program version to 6.0.1125.
Avast ran last night and did NOT flag the data file in my backups.
Although I cannot tell where in the Avast to see exactly which drives it scanned, the “amount of data tested” suggests Avast scanned everything, that is, my two internal hard drives and the external backup drive with the 140 copies of the file in question.
Thank you everyone for the help & advice.