I'm also with two asus ZE520KL handsets, imei null after downgrade ...
I bought the ufi to try to refaze them, because I tried to change the android to 6.0.1 and 7.0 several versions of the site and none are coming back, I tried to restore the baseband.bin available on the website but did not give ...
I was answered here only once now I am without support to solve this problem,
Because I already gave root in the device and unlocked the bootloader, and everything I try is not successful
One of the developers of the UFi who spoke to me is very intelligent, but does not respond anymore.
And we are waiting for the new update to try because the box does not have support for the platform of the device (ze520KL processor cualcomm msm 8953) the box says that it worked but you restart the device and it is the same way
And I'm already thanking anyone who gives us help