I am using Zoiper Biz for Windows 2.0 with g729 and have been for some time now. It is for a small call center with two operators on separate PC's. From around 3 months ago a new issue a raised where after the user has answered the call and speak they can hear a dial tone. It happens only when the Zoiper user speaks into the microphone and makes it impossible to have a conversation.
It does not happen with all calls just sometimes. I have tried; reinstall, removing config file, Only having one service activated at the one time, changing STUN to on and off and changing pretty much every setting available but to no avail.