Portfolio Page Slider Does Not Always Load

I have one more issue I am having. I can’t replicate it always but at times, when clicking on a portfolio thumb to take you to portfolio page, when the page is set for Full Width (Slider) because of multiple images, sometimes the 1st image does not load, after the delay, the 2nd image will load with the slider finally appearing. Do you know why this is happening? the domain again is http://www.wheatonmulch.com

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