Loader (spinner) not showing in Chrome if not in debug mode

I have a function I call on form submit and once result is received by ajax. The function is to show or hide loader gif on a page.

It works well in Firefox and IE, while in Chrome the laoder doesn't show/ form doesn't hide. However if I do js debugging in the console in Chrome the loader and form show/ hide works well.

Quite strange it doesn't work without debugging. I have no errors in the console at any time.

The function:

function loader2(loaderClass, destinationClass, showLoader) {
    var $loading = $(loaderClass).hide();
    var $form = $(destinationClass).show();
    if (showLoader) {
        $loading.slideDown(500);
        $form.hide();
    } else {
        $loading.hide();
        $form.slideDown(500);
    }
}