<p>You could try the following hack/patch:</p>

<pre><code>--- a/modules/uac_registrant/reg_records.c
+++ b/modules/uac_registrant/reg_records.c
@@ -84,7 +84,7 @@ static void gen_call_id_ftag(str *aor, str *now, str *call_id_ftag)
        if(now-&gt;s &amp;&amp; now-&gt;len)
                src[i++] = *now;

-       MD5StringArray(call_id_ftag-&gt;s, src, i);
+       MD5StringArray(call_id_ftag-&gt;s, src, 1);
        return;
 }
</code></pre>

<p>This should keep the Call-ID header the same, but CSeq most likely will be reset and I don't know how your PBX will react to it.</p>

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