Sip phones continue to ring after hang up

Asterisk Asterisk Support
1

Hi, i’m building an asterisk server with an digium TDM410 (2 FXO)
Asterisk 1.4.20-1
zaptel-1.4.10.1

All incomings and outcomings calls works very well, but here is my problem

When i got an incoming call , if the caller hangsup before i answer, my sip phones continue to ring. The call follow the dialplan to the end.

i remarked that when i try a “setup-pstn” i works , but if i restart the service asterisk , the problem occurs.

Thank you for your help
Pascal