Propulsion Slider stalls

I’ve had a website using the Propulsion theme for several years and, in the last 6 months or so, I’ve noticed that the homepage slider (and the slider on product pages) is very sluggish in bringing up the actual images. Sometimes it loads them after 20 seconds, sometimes it never loads them all all. Occasionally, it will show the images without issue on the first try.

Try http://selectbilliards.com/product/predator-sport-ii-ice-wrap/ and see if the slider pops up. I usually get an image for a brief moment, then the slider area goes grey with a “loading” icon in front of it.

I can’t figure out what things to change to address this issue. I’m running Propulsion v2.5 and WooCommerce v3.1 (both as up-to-date as is currently possible).

Any thoughts on what can be done to make the slider work properly every time? Thank you.