I reinstalled stock firmware by nokia software updater and updated to 8.1 by wifi.
There is no bug no lag no battey drain.
Camera works well. No error no lag no heat no reboot.
I can't believe it. It's even faster than wp8.
But wifi eap-tls/ peap is still not available.
8.1 supports and recognizes eap but cannot connect to office wifi.
I think it's not bug but lack of support.
So I should use hotspot with pc ethernet.
There is no bug no lag no battey drain.
Camera works well. No error no lag no heat no reboot.
I can't believe it. It's even faster than wp8.
But wifi eap-tls/ peap is still not available.
8.1 supports and recognizes eap but cannot connect to office wifi.
I think it's not bug but lack of support.
So I should use hotspot with pc ethernet.