Keep encoding when request is handled by irule

During troubleshooting I did simples possible condition to replicate issue also for other endpoint. As I received report for specific endpoint where custom irule was written I covered another endpoint to replicate issue. And it's behave same. Below is part of irule.

when HTTP_REQUEST {
catch {
    		    if { [HTTP::uri] starts_with "/api/test/endpoint" } {
			        log local0. "DEBUG: Edit URL detected"
			        set UrlEdit 1
    		    }
            }

    		if { [HTTP::header value Content-Length] > 0 } then {
    		    log local0. "DEBUG: myapp - collecting data for edit URL"
    		    HTTP::collect [HTTP::header Content-Length]
    		}
}
when HTTP_REQUEST_DATA {

  catch {
    if { $UrlEdit } {  
        #set editpayload [HTTP::payload]
        #binary scan $editpayload [HTTP::payload]
        #HTTP::payload replace 0 [HTTP::header "Content-Length"] $editpayload
        log local0. "DEBUG: myapp: edit page detected with payload: $editpayload"
        HTTP::release
    }
  }
}

Part of the payload is:

--data-raw '{"customer":{"name":"漢字__字汉__"

There is no compression. Only small payload is forwarded.

At the end in application is string with Chinese characters represent as 漢字字汉

If we take first character 漢 in UTF-8 it is 0xE6 0xBC 0xA2 what is converted back as E6 (æ) + BC (¼) +  A2(¢). In summary 漢 = æ¼¢.

Adding also part of the log from ltm. Characters were already converted:

{"customer":{"name":"漢�__��__