I've same problem, audio work only a way, internal to external. All port forwarded correctly, same stun server used. Windows firewall down.
I know that the problem is the router, becouse witohout router firewall all work good. But there is not a solution for this. I read all post forum, nothing todo. my log:
07:46:57.640 MediaServerReporting::RTPReceiver [MS105000] Call(4) Ext.100: No RTP packets were received on 00000008@:remoteAddr=217.202.104.128:54200,extAddr=87.6.59.135:10233,localAddr=0.0.0.0:9010
07:46:53.578 StratLink:

nHangUp [CM104001] Call(4): Ext.100 hung up call; cause: BYE; reason: SIP;description="User Hung Up"
07:46:34.140 ServRegs:

nAdd [CM113002] Registered: Ext.101
07:46:32.406 ServRegs::checkExpiration [CM113000] Registration for sip:
[email protected]:5060 has expired
07:46:25.531 CallLegImpl:

nConnected [CM103001] Call(4): Created audio channel for Ext.100 (217.202.104.128:54200) with Media Server (87.6.59.135:10233)
07:46:25.531 StratInOut:

nConnected [CM104005] Call(4): Setup completed for call from Ext.101 to Ext.100
07:46:25.531 CallLegImpl:
nConnected [CM103001] Call(4): Created audio channel for Ext.101 (192.168.1.102:9000) with Media Server (87.6.59.135:10231)
07:46:21.546 CallConf:

nProvisional [CM103003] Call(4): Ext.100 is ringing
07:46:16.968 CallConf:

nIncoming [CM103002] Call(4): Incoming call from 101 (Ext.101) to sip:
[email protected]:5060
HELP PLEASE.. :cry: