My FreeSWITCH is behind nat, and I have calls coming in from internet on port 5060. This works great after I got the IP range set in acl.conf.xml.

But the calls get hung up after 40-50 seconds into the call for no reason at all. But after I restart FreeSWITCH, this annoying behaviour doesn't happen.
I traced both cases, when the call is hung up here:
http://pastebin.freeswitch.org/4784 
It looks like FreeSWITCH is resending SIP/2.0 200 OK   for some reason, until the other end gives up and sends a BYE sip:Unknown@81.201.82.28 SIP/2.0

But after a restart, FreeSWITCH behaves much better, and the call goes on until one of the parties hang up normally:
http://pastebin.freeswitch.org/4785 

I am not sure if this is a bug, or a misconfiguration of FreeSWITCH

FreeSWITCH Version 1.0.trunk (8900)

Ivan