Airplane mode always on

Dec 17, 2016
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#1
Hello there.
Bought my second used ZUK Z1 and the previous owner told me that it works fine but for the airplane mode.
So got the phone, flashed with QFIL two different CM12.1 images but the problem persists. It reads the SIM card but there is no signal reception as if the antenna is shut down.
I have read that quite many owners are faced with this bug, so was wonderig whether anyone can offer any idea apart from changing the motherboard :)

Thanks