[Q] Wifi Problem Hangs Mobile topic

Hey Guys
I've a Complicated problem
at first i've nexus 5 lollipop 5.0.1 version
while i was using it today it freezes and Wifi turn off and didn't response
then i've restated it
I found
- missed apps from homepage
-hangs and freezes
- can't connect to the Wifi it hangs and freezes the phone at all
- it restarts some times by it self
- hanging and freezing

at first i've done
Factory reset , wipe data/cach

nothing happened

and this happens at soft mode to by little than normal mode

then I thought that the problem is Lollipop software

then i've Downgraded it to 4.4.4 .. Stockrom kitkat
the mobile become smooth acts normal
but still the Wifi problem persists
it's not turning on
and it hangs and freezes the mobile while turning on
and at the Sittings menu "kitkat"
wifi is on and i cant turn it of it became on without any activation
and I've done factory reset and wipe
after downgrade and the problem still persists