Voice Call is not working

[rider8581]

Good day!
Thank you for your contribution.

I deployed my own server and built the android app to connect my own server.
The server has been built in docker mode and I deployed retund on my another server as a docker container.
However, the voice call is not working well.
I am testing with several mobiles in different locations and emulator but in some cases, they are not working.
On receiver side, it rings and then accept but it keeps showing "connecting ...".
Some guys, it depends on the receiver or caller's NAT type.
Would you kindly guide me how I can debug this issue?

Also, the connection speed is very slow. It is taking 10 ~ 30 seconds in case they work. How can I improve this speed? Maybe are there any delay param on wire server or mobile app?

Kindly guide me please.
Thank you.