I can't find any discussion of Android File Transfer here. It is now unusable with my main computer, a Mac Mini running Catalina OS. The app just freezes and I have to force-quit. Reinstalling it just give me an error message that it's incompatible with computer.
AFT is without doubt one of the weakest garbage applications still littering the IT world, even when it 'works'.
UPDATE:
You do not have to use AFT.
I found
OpenMTP. I just transferred a few GBs of flac files from my Catalina Mac to my FiiO M11Pro - both internal and SD - quickly, smoothly, crashlessly. It almost seems like the 21st century with this thing!
It's free and open-source. It's described as some developer's answer to 'hopelessly outdated' AFT and its freezes and crashes. And it works with 64-bit Mac OS, at least in my case.
Hope it works for you guys.