Slides are stacked, and visible, on intial page load. How to prevent?

[NJWebDesign]

All of the slides in our BX slider are stacked, and visible, on initial page load. How can I prevent this and is there a way to display a "loading" gif or fontawesome spinner instead, whilst the images load?

I've tried preloadImages: 'visible' and preloadImages: 'all' but neither seemed to make any difference.

Example page: http://www.torrswarrenhotel.co.uk/index.php

Hope someone can help. Thank you. NJ

[NJWebDesign]

Still having problems with this, plus it's affecting other sites too that use BX Slider: https://www.tradmusic.com