Internet Explorer Javascript - Working Properly After Opening Inspector

Question

I've reviewed similar questions without any luck: Why Javascript Only Works After Opening Developer Tools in IE Once

Essentially, I have a page with an area that can animate a vest: Vagalume Innovation Page

You can animate the vest with a set of options below it. In IE (all versions) it only works if you press it twice. For example, press "Slow Flash" and then "Constant" and it takes two times before it registers.

As soon as I open Developer Tools, the problem goes away.

There are no console logs to deal with, so I'm very confused. Any insight would be greatly appreciated!

Edit

Here is the code that changes the flashing pattern:

if ($('.demo-trigger').length) {
    $('.demo-trigger').on('click', function(event) {
        event.preventDefault();
        clearInterval(intervalId);

        var trigger = $(this),
            pat     = trigger.data('pattern'),
            timer   = false;

        _lights.removeClass().removeAttr('class').addClass(pat);

        $('.demo-trigger').removeClass('active');
        trigger.addClass('active');         
    });
};