[SR-Users] Unknown $dlg(h_entry) and $dlg(h_id) in dialog

[Никитенко Виталий]

Hi i have kamailio 4.2, dialog module with parametr
modparam("dialog", "dlg_flag", 5)
modparam("dialog", "enable_stats", 1)
modparam("dialog", "profiles_with_value", "caller")
modparam("dialog", "dlg_match_mode", 1)
modparam("dialog", "default_timeout", 3600)
modparam("dialog", "timeout_noreset", 1)
modparam("dialog", "send_bye", 1)
modparam("dialog", "timeout_avp", "$avp(i:4242)")
modparam("dialog", "db_url", DBURL)
modparam("dialog", "db_mode", 0)

in event_route[tm:local-request] i use 
    if(is_known_dlg()) {
        xlog("L_INFO","DIALOG IS KNOWN $dlg(h_entry)::$dlg(h_id)) I
    }

And when call drop by timeout, sometimes in log i see 
/usr/local/sbin/kamailio[21144]: INFO: <script>: DIALOG IS KNOWN <null>::<null>

But usually this string in log file i see as "DIALOG IS KNOWN 3452::3334"

Why it may be? when the $dlg(h_entry)::$dlg(h_id) is not known, I can not track $DLG_lifetime.
Different between unsuccessful and successful call i dont see