I've the sip service configured on an android mobile with zoiper and I can hear/talk fine.
My problem is that when receiving calls, pick-up screen is presented and I can swipe to answer, but then I get a delay up to 20 seconds for talk screen to appear and being able to hear/talk. The caller get silence during that time (ringing stops). I've seen that if I restart the phone, the lag dissapear, and it seems to come back along with uptime in the phone.
Somebody know what could be happening?