Conflict with Divi?

I’ve been using Fly Cart on this site fir a few months now, and it’s been fine. However, lately there’s been a conflict where when the fly cart opens there’s a rather huge gap between the quantity field and the plus button. Worse yet, instead of adding or subtracting one item to the cart, it adds or deletes two.

I’m using Divi and whether it’s with a child theme or not, the problem persists. Switched to both Twenty Fifteen as well as Twenty Seventeen and the problem goes away. Also I’m using WP-Rocket but deactivating that does not remove the issue.

The page I need help with: [log in to see the link]