Slide Show Freezing

I have created two slideshows with 21 images in each. The slideshow often freezes and I have to click on a thumbnail image to get it to resume playing. Should my images be a certain size or format? I have used .png images and is there anything I can do in the setting panel to stop the freezing?

You can view the slideshow here (this is not ready for public viewing so please keep that in mind). I posted it to test the slideshow functionality
https://www.hanleywood.com/news-opinions/construction-wire/bba-winners

https://www.ads-software.com/plugins/grand-media/