One thing that helped me when I was troubleshooting the 2.4Ghz and USB3.0 issue was making sure I had the correct country code set in my netwrok/wifi settings. Wifi channels and signal strength differ from country to country. When I was pinning my astroberry to only run in 5Ghz hotspot mode and only connect to my 5Ghz home wifi SSID, I could not reliably connect after reboots. I read in another forum about the country code setting.

Run raspi-config and go to "Localisation Options" then "Change Wi-fi Country". Set it your country.

Mine has be very stable since I made this change. HTH

Read More...