I was able to do some further testing with this, and tracked down the issue (though I believe it's a bug)...
When setting up the slide for the Tablet breakpoint, we add on a copy of the image used on the desktop view, that loads after 1.7 seconds. We do not need this image displayed on the Desktop breakpoint, so when working on the tablet view, we select the image, right-click and select "Exclude from other views". This then moves the image off the viewing area on the Desktop view.
When playing around, I manually tried to move the image off the Desktop viewing area, but noticed at its full size, I could only move it partially over (some still appeared in the view, while some was out of the frame). I then just re-sized the image so that it was small enough to be out of the viewing area. When I republished and tested the published copy, that slide no longer had an issue. I worked through the simulation one slide at a time (republishing between fixing each slide and testing) and as I did, the issue was resolved for the slide updated.
So........ Basically, the Exclude from other Views seems to move the image to a position that causes some load issue as a browser tries to load the slide. To correct the issue will take some extra steps/clicks, but at least it works. I plan on reporting the bug to Adobe shortly.