I am also facing this exact problem and missing a lot of calls and SMS and like Torpedro1978 said the signal flickers from zero to 3-4 bars. This is really annoying. I am on BB ROM with Ardatdat's Kernel v4.2 Beta 6. Please help.
Try kenerl 4.0
Worked for me.
Sent from my GT-I9103 using xda premium