I've the old bootloader (I'm sure!) and I flashed the XXUBMH1 modem as recommended here and I had connection problems so I've upgraded to "XXUGNE5 GSM modem only".
With it I had connection problems too, so I tried "Wifi fix/NON-HLOS I9505_XXUGNE5_WiFi_FIX" and problems remains.
Now I've upgraded...