When I try to add a layer to my slide, it erases everything. I can add a background only and then save with no problem. However, when I try adding a layer is when everything erases.
As mentioned in the other ticket you have commented to, this is most likely a conflict issue with a 3rd party item on your installation or a server configuration problem.
Please try to temporary disable other plugins and switch to a default theme to see if that solves the issue. Please also check the LayerSlider System Status for any error messages.