Default Need help , weird problem on downgrade

So long story short:

when i downgrade my phone to 4.2.2 , phone is not stable at all , it only works 20-30 seconds and then it restarts .
i tried both tot and kdz method , also did factory reset . but still same . phone only works on kitkat : official 24A/25A(newest firmware) , or some custom roms on kitkat . but JB doesn't work anymore .

some time ago it worked , but for now it doesn't .

So what should i do? i can't understand what's problem . should i try to do that on other computer or with other usb or whatever?

I need downgrade, because my cell radio is off on kitkat and i'm not getting signal at all , radio is disabled (can't figure out whats wrong with this)

maybe i have some hardware problem and it's not software?