Without receiving any help from you, I tried to solve the problem myself. So far, not successfully.
1. I turned off all the plug-ins.
2. Tried to install on a clean theme.
I need your help on this. List of problems:
1. Changes in the slider are not saving.
2. The second slider’s not working.
3. The preview does not show all the elements added to the slide.
Your slides work until you add a few new items or remove old items.
Perhaps the problem is that the site runs on nginx. Please help.