Slider class slide-thumb-active

I have a custom slider that uses thumbnails with text to navigate my slider similar to what is shown in the video ( at around the 13min mark). My active slide relative style targets the div and adds a border when .slide-thumb-active class is dynamically added to the slide thumb.

I followed this example to implement with the current version of Cwicly and everything works well, except that I cannot seem to style the first active slide, when the slider initiates I see .swiper-slide-active on the first slide, and when it switches to the next slide, the .swiper-slide-active class remains on the first thumbnail, and only then does .slide-thumb-active get added to the current thumbnail - if I then click back to the first slide, it adds the class .slide-thumb-active and my active styles then apply.

How do I apply my active slide style so that it applies to the first slide and removes upon switching to the next slide, where the next slide then shows as active?