No es por desanimar, pero esto lo acabo de sacar de xda:
"I have the same problem with calls going silent for about 5 seconds intermittently. I installed the latest patch that was supposed to improve call stability but within 3 days after update the problem has occurred again. So frustrating"
Me estoy planteando ir al ECI esta tarde y pedir la devolución... aunq seguro que salen con alguna excusa