Client Slider doesnt work

Hello,

unfortunatelly my client slider doesnt work.
When i click on the arrows nothing happens. Also when i try to move the slider with the mouse i can move them but after releasing the mouse it slides back to start.

I tried many revisions of the site also the clean demo installation.
Maybe a missing plugin or something else?

(I will send link to the site private if u need it)

Thank you in advance.