Default [Q] Microphone mute in call

My problem is that sometimes the microphone is cut (mute) during the call. Its mean that other side dont hear me but I hear everything. Sometimes I must hang up and call again and sometimes after maybe 10 second is all ok. But one time I hang up, call again but the person still does not hear me. So I must wait a few minute and call the person again.

I tried 3 room - stock, CM 10.2.1 stable and CM 11 beta but it doesnt help.

Do you have some ideas?

Thank you for your reply.