Seems likely you have 2 definitions of your form in html (or that is the javascript version of the form, and the html version is different). We parse the form at build time, from HTML ONLY, and if there are two copies, only one will win. If you update only the JS, the HTML will still be our source of truth.
This article talks about how to debug form misbehavior and I’d bet my next paycheck that the answer is in there 
[Support Guide] Form problems, form debugging, 404 when submitting