Asp.net MVC renders 2 "form action" statements for the same form when in responsive mode

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MVC

ASP.NET4

ASP.net MVC App. Visual Studio 2022

App runs fine in desktop mode.

This line:

@using (@Html.BeginForm("SubmitForm", "Home", FormMethod.Post, new { id = "subform", verify = "Y" }))

is generated correctly as:

<form action="/Home/SubmitForm" id="subform" method="post" verify="Y">

when I inspect the page.

However, if I try to emulate a cell phone, the generated html is:

<form action="/Home/SubmitForm" id="subform" method="post">                    <form  action="javascript:submitform()" method="POST" style="display:none;visibility:hidden;">

There is no javascript function called "submitform" so of course it fails.

What I have tried:

I did add an empty "submitform" function but that did not solve the issue.
How do I stop this javascript reference from being generated in error?