I have a 3cx system set up behind a SonicWall TZ200 with all necessary ports forwarded. I have keep alives enabled on the 3cx system. I have set the TCP and UDP timeout time to a reasonable number. Everything will be working fine and then randomly when dialing in a user will get a busy signal, hang up and redial and call goes right through. Log never shows that a failure has occurred, but the CDR states that the line was indeed busy. Nobody will be on the line, internal or external when this behavior occurs. Has anyone else seen anything like this?