NAT Issue - One Way Sound

Goog Morning,
i have being googling for many hours without any solution to my probleme. My english is very poor.
Here is my network diagram:

Public IP(Internet)<---->AdslModem<---->Mikrotik<---->(My local Network) switch to Asterisk server and Clients

My Configs
1- I have define DMZ on my Modem to send all incoming trafics to mikrotik
2-On Mikrotik, i have forwaded SIP port 5060 and RTP(10000-20000) to Asterisk Server

My succesful scenarios with 2 way sound on call
1-Two clients outside my Local Network accesing via my PUBLIC IP
2-Two Clients inside my Network accesing via the LOCAL IP of my asterisk server

Unsuccesful Scenarios(One way sound)
1- client1 outside my local network accesing with my PUBLIC IP and client2 inside my local network connecting with my PUBLIC IP. client1 listens to client2 but client2 does not listen client1

2- Both clients inside my network and connecting using my public IP but non of them listen to each other.

Please i need your help to resolve the two unsuccesful scenarios

Disable direct media or set directmedia=nonat. If you are not using direct media, please provide the SDP from the thee cases.