gps problem

hi all, ive not long had my brand new z5 and the gps doesn't work, I would send it back but as the rear glass broke (in my pocket) I cant return it. I have used a few gps fix/test apps, the service menu, many attempts at agps updates etc but I still get around 20 satellites in view but never any fixes. Is there anything I can do? I'm guessing the antenna is ok as it can see the satellites?. tried a factory reset but still no joy. is my only option to root and go custom rom?

any advice is greatly appreciated

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