Adapting a theme, scroll broke

[brokendrive]

Hi, this might be in the wrong place, please let me know if so

I have been using a new theme and made some modifications in the files. At some point, the scroll arrows in quickview and final product view broke, but work in all other places. I have been able to warp the theme with html and css, but quite sure how to fix this one as I think it deals with javascript. I do generally know javascript but not sure where to edit what file

The problem: If you go to quick view on any product at https://santoryu.com/  you will see that the arrows dont work.

Also, if you zoom in to see the full images in an example product, the arrows dont work either. In fact they aren't even visible (i can move them and fix through CSS but not sure if that would further break the click operations).

Can someone please help me fix this? I am willing to modify code or w/e is needed