I have not occuring this problem with previous version of LTE modem such as VJUFNC1 or XXUFNB9 or older. Anyone knows what causes it ? My current ROM is ECHOE V20.
After I have flashed XXUFNC5 or XXUFNC9 LTE modem, I find that it will display "baseband unknown" after the phone has booted and the cellular function is disabled. I need to wait about more than 10 minutes and then the baseband version can be correctly displayed and functioning as normal.