find an dreplace XML Value with irule

I made a couple of tweaks to the script below:

when HTTP_REQUEST {

log local0. "Inside Request"

if { [HTTP::host] contains "dev.integration.services.7-5.identifythebest.com" } {

if {[HTTP::method] eq "POST" && [HTTP::header value Content-Type] contains "text/xml"}{

log local0. "Inside IF"

HTTP::collect [HTTP::header Content-Length]

HTTP::header remove "Accept-Encoding"

HTTP::collect

}

}

}

when HTTP_REQUEST_DATA {

log local0. "Inside Request_data"

set offset [string first {"SSN">} [HTTP::payload]]

set length [expr {[string first {<} [HTTP::payload] $offset] - $offset}]

log local0. "Offset $offset length $length"

log local0. "Replacing [HTTP::payload $offset $length]"

log local0. [HTTP::payload]

HTTP::payload replace $offset $length {"SSN">--}

}

Now I get the following output:

Aug 20 07:17:49 local/tmm info tmm[5162]: Rule _xml_scrubber : Inside Request

Aug 20 07:17:49 local/tmm info tmm[5162]: Rule _xml_scrubber : Inside Request

Aug 20 07:17:49 local/tmm info tmm[5162]: Rule _xml_scrubber : Inside IF

Aug 20 07:17:50 local/tmm info tmm[5162]: Rule _xml_scrubber : Inside Request_data

Aug 20 07:17:50 local/tmm info tmm[5162]: Rule _xml_scrubber : Offset 1138 length 17

Aug 20 07:17:50 local/tmm info tmm[5162]: Rule _xml_scrubber : Replacing "SSN">555-55-5555

Aug 20 07:17:50 local/tmm info tmm[5162]: Rule _xml_scrubber : 91f0f42d-8529-4725-9429-9b2edcb92abaTa13oPint3rgrat10nabdd33e8-f7ef-4808-b06b-6d06d2309fdb25122cb16ddd9-3e71-4337-b593-cb9a8bb9c48e7de4511aa-e973-4ab6-a224-02a841

From looking at a packet capture the whole post is in one packet, but the output of the payload appears truncated. any advice?