asterisk users - Feb 2005 - ZAP channel on TE410P doesn't hang up (Plain Text this time)

Hello * users

Sorry I forgot to send the mail in plain text the first time...

I've have a rather disturbing problem, which I don't know how to debug
or
how to solve, but first a brief description of the set up.

One Asterisk server with a TE410P card installed (first line used on this
only), and a number of Wellgate 3504A (4 port FXS devices with SIP
firmware). There is no connection from the Asterisk server to the outside
world or any other IPTEL providers. The server only acts as a PABX and PSTN
gateway for the SIP devices. 

Now the problem; sometimes the ZAP line isn't disconnected properly, I
don't
know what causes this and ?haven't been able to reproduce this behaviour,
which is why I haven't got a clue how to debug the problem. The way I came
across this issue was by examining CDR files from our telco provider, which
showed that some calls had been "hanging" for over 24 hours. The
"funny"
thing is that the major part of these hanging calls was to another Asterisk
server PSTN->PSTN (Almost same set up) and as far as I've been able to
interpret the calls have been answered by Asterisk Voicemail (I don't know
if this is of any importance). 
Have anybody experienced the same behaviour or got any ideas to what can be
done, as this gets rather expensive over time.

I've googled a lot to find any clues, but only found some similar problems
on the X100P board.
As a side note I've now implemented an AbsoluteTimeout for the call, I know
this isn't a solution but merely a workaround.

Please let me know which configs or logs to provide, any help is greatly
appreciated. 


Kind regards,
Mickey Binder