Shirt image displays over top of basket

When I have the basket open the shirt zoom window is displayed over top of the basket when hovering over that particular area.

Any ideas on how to fix this?

I’ve tried making the z-index higher, but that did not work. I think it may be because of overflow:hidden but I am not too sure…

link : https://greydonsquare.net/gs/merch/

https://www.ads-software.com/plugins/wp-spreadplugin/