$.cookie is not a function from form.js with block cache I am getting this error if I turn my block caches on.
I have traced back the origin back to Drupal core form.js but can't seem to see what's going on here.
Any ideas?

Here is the debug:

form.js?v=7.56:69 Uncaught TypeError: $.cookie is not a function
at String.&lt;anonymous&gt; (form.js?v=7.56:69)
at Function.each (jquery.min.js?v=1.7.2:2)
at HTMLFormElement.&lt;anonymous&gt; (form.js?v=7.56:67)
at Function.each (jquery.min.js?v=1.7.2:2)
at $.fn.init.each (jquery.min.js?v=1.7.2:2)
at $.fn.init.$.fn.once (jquery.once.js?v=1.2:55)
at Object.attach (form.js?v=7.56:65)
at Object.&lt;anonymous&gt; (drupal.js?p3kpc3:76)
at Function.each (jquery.min.js?v=1.7.2:2)
at Object.Drupal.attachBehaviors (drupal.js?p3kpc3:74)


Update: I think I am isolated this problem to a webform in a block on the page. If I get rid of that form, the error goes away. Also, this error doesn't happen every single time. Sometimes I have to change browser or open in incognito for it to crash, and then it happens repeatedly.

I can see that jquery.cookie is there when it works. But when there is a crash and I see the page source it's not there, so somehow it seems it's failing to load and when it happens I get the error. I am using JQuery Update (1.7).
This happens sometimes as $.cookie function is not supported. In those case you can try following approach.
Place this code in your JavaScript file
function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays*24*60*60*1000));
  var expires = &quot;expires=&quot;+ d.toUTCString();
  document.cookie = cname + &quot;=&quot; + cvalue + &quot;;&quot; + expires + &quot;;path=/&quot;;
}

function getCookie(cname) {
  var name = cname + &quot;=&quot;;
  var decodedCookie = decodeURIComponent(document.cookie);
  var ca = decodedCookie.split(';');
  for (var i = 0; i var c = ca[i];
  while (c.charAt(0) == ' ') {
    c = c.substring(1);
  }
  if (c.indexOf(name) == 0) {
    return c.substring(name.length, c.length);
  }
}
return &quot;&quot;;
}

Then you can use, setCookie(cname, cvalue, exdays) and getCookie(cname) to use set and get cookie functionalities instead of $.cookie.
Hope this works.