Every call ends after 12 sec

Every call i make from external network is being automatically ended after ~12 seconds. The connection is fine - a conversation can be made but for some reason cannot talk more then 12 seconds. Here is a short description of my network.
I have Asus RT-N66U which doesn’t support SIP-ALG. Also Cisco SPA3102 and a RaspberryPi which runs FreePBX

The router forwards UDP port 5800 to my raspberry successfully. I should mention that i have edited /etc/asterisk/rtp.conf and changed two lines:
The router is also setup to forward UDP ports from 11000 up to 20000 to freepbx.

As a client when not at home i use csipsimple. I tried changing the “RTP port” from -1 to 11000 but it doesn’t help.
csipsimple registers itself as extension 1000 which is configured in freepbx as being behind nat (nat is set to yes).
Under “Asterisk SIP Settings” i have:
NAT yes
IP Configuration Static IP
External IP
Local Networks /

At the end here is a log from asterisk CLI: http://pastebin.com/6B7KKf2Z

I should add that when using the local network there is no such “limit”.

Asterisk can’t establish continuity on the RTP, even though you can hear the speech.

This is a NAT issue with your router. Also, you don’t need 10,000 ports open, you only need 4 per concurrent call (2 call legs two rtcp streams).

Lastly, 5800 is non standard SIP port. If you are translating this in the router using PNAT this is the start of your trouble.