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Call standby must be always active, otherwise you'll miss calls due to no coverage. If you wanna disable radio go on Airplane mode.
There will be no fix coming. Flash your phone to older fimrware. Sorry to say that but they haven't fixed them for 1.5 year, so there will be no fix.
I'm sorry to hear that but you could perhaps flash a custom ROM, keep in mind that the Xperia Z was released February 2013 with android 4.1.2, although we want our phones to be on this perpetual update cycle it's unlikely, not even Nexus devices get perpetual updates.