I am having the exact same issue, among others. This slider was working great and I had no problems with it. It was exactly what I needed. All of a sudden it is completely bugged out on the back end. None of the thumbnails show up, even after regenerating new thumbnails. They’re just blank??? These thumbnails were working just fine before. There are a number of other issues I’m having as well. I cannot click on any of the settings tabs after switching to slider settings. All of my wrapper settings and transition speed settings have disappeared on the slide settings page, and no matter how many times I save it, none of the toggles stay toggled. I cannot see the “text” display of the Slide Info even though it’s selected (screenshot linked), although it didn’t even want to do that at first. The transition settings on one of the sliders isn’t even being set correctly. I have three separate sliders, they are all set to normal slide transition, but one of them has decided it would rather do a fade transition, which is why I’m here instead of just dealing with how incredibly buggy this thing is.
The sliders are on a production website so I cannot disable other plugins until it works. Here is a screen shot of what I see with the thumbnails and buggy slide info box: https://drive.google.com/open?id=0B01M2czhjMbfMFNFSEpYNllBWnc
And here is a screenshot of the permanently disabled settings and toggles: https://drive.google.com/open?id=0B01M2czhjMbfUW1rd2RMTThGLUE
