If you are reading this , it means you are victim of this JS error which you see in your browser console on form submit. I stuck with this and burned a whole day in investigating the root cause of this error. I went through many posts but nothing worked out in my scenario.
I went through few posts which are given below and I think you should take a look at them before you continue here ( if you are not already gone through)
https://github.com/jquery-validation/jquery-validation/issues/1829
https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9951527639601970
(adsbygoogle = window.adsbygoogle || []).push({});
if you are still here… means your issue is not resolved yet. Now, let’s explore what I did to fix this issue.
I opened OuterLayout.cshtml file and noticed that the Jquery was referenced after the @Html.RenderFormScripts() method call.
This was not loading the jquery.validate and other required files.
I just referenced some of the required JS files before the @Html.RenderFormScripts() method call. 
This resolved the error and form submitted successfully. I am hoping that this can help some in their Sitcore journey.
SitecoreTricks 