Forms generated script indexof undefined

Hi,

I'm having an issue with clicking buttons in episerver forms - buttons in this case are the submit, next step etc. form elements.

I've set up "@Html.RequiredClientResources("Header")" just before the closing head tag, and "@Html.RequiredClientResources("Footer")" just before the closing body tag.

The issue is only present when the "@Html.RequiredClientResources("Footer")" is in the HTML document, if I remove it - everything works. However we have other solutions that require the "@Html.RequiredClientResources("Footer")" to be present. I've tried to use both the built in jQuery, and an external source without any luck - the stacktrace below is from using the external source.

The console error is the following:

Uncaught TypeError: Cannot read property 'indexOf' of undefined
at WebResource.axd?d=Tz…37213340560000000:1
at HTMLDivElement.<anonymous> (WebResource.axd?d=Tz…37213340560000000:1)
at Function.each (jquery-3.3.1.js:354)
at jQuery.fn.init.each (jquery-3.3.1.js:189)
at h (WebResource.axd?d=Tz…37213340560000000:1)
at HTMLButtonElement.t (WebResource.axd?d=Tz…37213340560000000:1)
at HTMLButtonElement.dispatch (jquery-3.3.1.js:5183)
at HTMLButtonElement.elemData.handle (jquery-3.3.1.js:4991)

When you further inspect the error, it seems that 'n.DependencyInactiveElements' is undefined:

 return a.getAllDataElements(t).each(function(t, a) {
                            r = function(t, n) {
                                var r = e(t)
                                  , a = F(r)
                                  , s = i.getElementName(r)
                                  , l = r.attr("id") || s
                                  , d = o.getElementValidators(n.ValidationInfo, l)
                                  , m = !0;
                                r.removeClass("ValidationFail ValidationSuccess"),
                                a.hide();
                                var p = i.getElementValue(r);
                                if (n.DependencyInactiveElements -- ERROR IS HERE --.indexOf(s) < 0 && d instanceof Array && d.length > 0) {
                                    var f = o.validateFormValue(s, p, d)
                                      , u = e.grep(f, function(e) {
                                        return 0 == e.isValid
                                    })

Does anyone have any idea clue what the issue might be?

Best regards.