[Freeswitch-users] Problem bridging to an external mobile number

[ocset]

Hi

My configuration is a GXW4104 (IP 192.168.0.160) with two PSTN lines. 
The first line is a POTS line and the second line is a GSM gateway 
device. Both devices work correctly if I dial out but when I try and 
bridge between the two, nothing works as expected. The bridge is from 
the POTS line to a mobile number using the GSM gateway.

I have created the following bridge for the POTS line (phone numbers 
removed for privacy reasons)

<extension name="pots_line">
<condition field="destination_number" expression="^(xxxxxxxxxx)$">
<action application="bridge" 
data="sofia/internal/zzzzzzzzzz at 192.168.0.160:5062"/>
</condition>
</extension>

The bridge does eventually happen (long delay) but neither party can 
hear each other. Also, when I hang-up with one or both phones, the 
connection does not terminate and I have to reboot the GXW4104 to break 
the connection.

I have bought the Freeswitch books and this seems to be something that 
should easily work. I have not added any variables into the <extension> 
definition as this is a simple bridge.

What have I missed?

Thanks in advance