http_process_state_prepend - Invalid Action:0x109010

I did add some logging on the HTTP_RESPONSE, and logged the URI and HTTP status code, and the error message come up after that

: Status: 200 http_process_state_prepend - Invalid action:0x109010 (Server side: ...)

I also tried adding logging for the actual payload data, which seemed to have what looked like correct data in it. Here's the extra code I added:

when HTTP_RESPONSE {    
    if {$DEBUG} { log local0. "Uri: $uri" }
    if {$DEBUG} { log local0. "Status: [HTTP::status]" }

     Was returning here because collecting the payload messes up the response to the client (connection reset error). 
    return

     Trigger collection for up to 1MB of data
    if {[HTTP::header exists "Content-Length"] && [HTTP::header "Content-Length"] <= 1048576}{
        set content_length [HTTP::header "Content-Length"]
    } else {
        set content_length 1048576
    }
        if {$DEBUG} { log local0. "Content-Length: $content_length" }

     Check if $content_length is not set to 0
    if { $content_length > 0} {
        HTTP::collect $content_length
    }
}

when HTTP_RESPONSE_DATA {
     do stuff with the payload
    set payload [HTTP::payload]
    if {$DEBUG} { log local0. "Response Payload: '$payload'" }
}