Just finishing up: Problem solved.
Yes, I could access the "unable to scan" files in Sierra, High Sierra and Mojave.
I could be wrong, but as a long time Mac user, I think I just hadn't expected to click in a big blank space rather than on a more defined object.
I'm grateful that it works, although I now wonder about some of the files not scanned, e.g., what are Python framework test files, and are they necessary?