Quick tip if you ever start experiencing a drop in your ranking, more greyed out blocks of no reports in your statistics and sometimes no aircraft in your PiAware Skyview (1090 dump local live view). Your FlightAware USB stick may be on its way out.
After trying all kinds of software work to no avail (fresh Raspberry PI image with the latest updates including firmware and kernel updates) I finally changed out the USB stick for a new one, a USB Pro Stick Plus. And voila, there were all the aircraft in my live view!
My old USB Pro Stick lasted just one year, oh well. Hopefully my new USB Pro Stick Plus will do better.
By the way, the September Raspberry PI OS release with newest up-to-the-minute updates (sudo apt-get update, sudo apt-get dist-upgrade as well as sudo rpi-update) work flawlessly with PIAware 3.5.3 and 1090 dump 3.5.3. I ran all the OS updates prior to downloading PIAware.