[HELP]: Asterisk with ztdummy.ko calls do not disconnect

Asterisk 1.4.22.1
Zaptel-1.4.11
Freebsd 7.0-STABLE

Example of issue:

Call placed from extension 2001 to extension 2000. Call is terminated before extension 2000 picks up. Extension 2000 continues to ring until user picks up extension which then terminates the call with the following:

Connected to Asterisk 1.4.22.1 currently running on freebsd (pid = 31268)
Verbosity was 0 and is now 8
– Executing [2000@outgoing:1] Dial(“SIP/2001-00881000”, “Sip/2000”) in new stack
– Called 2000
– SIP/2000-00d50000 is ringing
– SIP/2000-00d50000 answered SIP/2001-00881000
== Spawn extension (outgoing, 2000, 1) exited non-zero on ‘SIP/2001-00881000’

If I unload ztdummy.ko everything acts correctly.

If any additional information is required I can post debug from SIP.

Thank you.