asterisk users - Jun 2005 - misdn and call hangup problem

Hi,

we test the misdn module together with beronet BN8S0 card.

We connect the pstn ISDN line to Port 1 and an ISDN phone to Port 2. 
That works great, the ISDN phone rings an we can make the call.

When the caller hangsup before call is answered  by the callee the call 
on Port 2 rings until end of day.
This is the extensions.conf part for this:
[incoming]
exten => _., 1, Dial(mISDN/g:ntports/${EXTEN})
exten => _., 2, Congestion
[outgoing]
exten => _., 1, Dial(mISDN/g:teports/${EXTEN})
exten => _., 2, Congestion

This problem does not occur when we call the isdn phone from a sip client.

Can anybody tell what is wrong with this configuration.

Thanks,
Kib