I started a test and after recording the hidden parameters "select_parcel", "product_delivery" was recorded in the form shown in the pictures.(no01, no02)


When I run the test I can see in the results that the parameters have no value:
[..]&select_parcel=&product_delivery%5B%5D=&[..]
do you know what reason can cause this?
more info of this POST:
POST /order?step=2 HTTP/1.1
Cookie: [..]
Content-Type: application/x-www-form-urlencoded
Content-Length: 325
Host: [..]
Referer: [..]?step=1&aid=3149
X-Forwarded-For: [..]
Connection: Keep-Alive
Accept: text/html, */*
Accept-Language: en-us, *
Accept-Encoding: compress, gzip, *
Pragma: no-cache
User-Agent: Mozilla/5.0 (compatible; WAPT; Windows)
another question is: is it possible to change the User-Agent/Browser?