How can I know if I have the 5G issue?
Reboot the phone and run a speedtest.
Now run a second, then third test. The speed gets slower and slower.
I have an up to 350Mb/s broadband at home, I could get around 180-200 Mb/s on first run and very quickly it'd go down to around 50 Mb/s.
I tried before and after 12.0.1 and I went from 160 Mb/s and falling on 12.0 to 250-260 on 12.0.1 on every speed tests.