Hi,
You should backup your database AND your files once in a while, it’s a basic when you work with a web application, in order to be able to restore a working version after mistakes made by you or users.
However, I made a similar mistake a while back and here’s how I corrected the CSS incompatibility of Scope indued by wordpress update.
At first, like you, I thought it was because of the overflow value of the “slides_container” that was set in hidden. When I changed it to visible, in the theme editor, the picture came back, but then started blinking.
So to stop the blinking I changed the position parameter to static in the “slides_control”.
BUT this made me realize that there is a much simpler solution (maybe not very clean but easier to apply) :
in the theme editor, in the home-imageslider.php, you just need to change EVERY <div class=slide> to <div class=slide style="position:static !important;"> and it should work
