Try to update parent web scenario.
Set 2 times same id for httpstepid

httptest.update

{
"httptestid": "62",
"name": "NormalNameTrunk",
"steps": [

{ "httpstepid": 281, "name": "Name3", "url": "http://mycompany.com", "status_codes": 200, "no": 1 }

,

{ "httpstepid": 281, "name": "Name4", "url": "http://mycompany.com", "status_codes": 200, "no": 1 }

]
}

Parent have 1 step with name Name3
Child don't have steps... And there is

Undefined index: stepscnt [httpconf.php:556 ? CView->render() ? include() in C:\xampp\htdocs\ZBX-8195-trunk\frontends\php\include\views\configuration.httpconf.list.php:81]