Two HTTP POST headers in a request after modifying the header -

despite title may suggest, not related common "preventing double post request" issue.

in application, add data on outgoing http traffic, , some websites, randomly encounter http post request has double-header, resulting in server termination, assume server doesn't understand request , decides cut me off. title says, i'm literally seeing 2 post headers in single request. happens when append custom http fields header. example, came across today when followed surveygizmo.com link, seen in trace @ bottom of post.

i cannot understand if it's browser that's doing funky because noticed i've modified data, or it's in lsp application causes happen.

when debug application, see intercepted request first time, when inject custom data. after that, don't see request anywhere except in wireshark, it's not can remediate double headers deleting redundant data.

things note looking @ trace:

• the data i'm appending 'custom-fieldn:'
• two almost-identical headers
• three double-crlf's in 1 single request header (how possible?)

the request:

post http://www.surveygizmo.com/s3/1212345/who-are-you http/1.1 host: www.surveygizmo.com custom-field1: usernamebob custom-field2: 2578291789 proxy-connection: keep-alive content-length: 836 cache-control: max-age=0 accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 origin: http://www.surveygizmo.com user-agent: mozilla/5.0 (windows nt 6.1; wow64) applewebkit/537.31 (khtml, gecko) chrome/26.0.1410.64 safari/537.31 content-type: multipart/form-data; boundary=----webkitformboundaryaqraa7zabicmt6jo referer: http://www.surveygizmo.com/s3/1212345/who-are-you accept-encoding: gzip,deflate,sdch accept-language: en-gb,en;q=0.8,en-us;q=0.6,ja;q=0.4 accept-charset: iso-8859-1,utf-8;q=0.7,*;q=0.3 cookie: sg-response-979523-1212345=0%3b1369154430_519ba37e477bc8.35524744%3b1369154430%3bpartial  post http://www.surveygizmo.com/s3/1212345/who-are-you http/1.1 host: www.surveygizmo.com custom-field1: usernamebob custom-field2: 2578291789 proxy-connection: keep-alive content-length: 836 cache-control: max-age=0 accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 origin: http://www.surveygizmo.com user-agent: mozilla/5.0 (windows nt 6.1; wow64) applewebkit/537.31 (khtml, gecko) chrome/26.0.1410.64 safari/537.31 content-type: multipart/form-data; boundary=----webkitformboundaryaqraa7zabicmt6jo referer: http://www.surveygizmo.com/s3/1212345/who-are-you accept-encoding: gzip,deflate accept-language: en-gb,en;q=0.8,en-us;q=0.6,ja;q=0.4 accept-charset: iso-8859-1,utf-8;q=0.7,*;q=0.3 cookie: sg-response-979523-1212345=0%3b1369154430_519ba37e477bc8.35524744%3b1369154430%3bpartial  ------webkitformboundaryaqraa7zabicmt6jo content-disposition: form-data; name="sg_navchoice"