iScroll v5.1.3 no longer works on website after iPhone is upgraded to iOS 13

I built a website (https://www.beaconhillprivatewealth.com) several years ago which uses iScroll 5.1.3 (https://github.com/cubiq/iscroll) to handle various scroll effects. Once an iPhone is upgraded to iOS 13, scrolling on my site no longer works. If you try to scroll a page, the browser behaves as if there is no content to scroll to, and bounces you back to the top of the page (actually, it never really leaves the top of the page).

Obviously something changed in iOS 13 (or Safari) which is making the site not work correctly, and my assumption is that the problem lies with iScroll, because all other websites work fine. I am not too familiar with how iScroll works exactly, but its all JavaScript. So what could have changed with iOS 13 with regards to JavaScript compatibility?

I looked up some articles regarding iOS 13, and found a few snippets in one article (https://medium.com/@firt/iphone-11-ipados-and-ios-13-for-pwas-and-web-development-5d5d9071cc49) related to scrolling:

Scrollbars are now draggable on iOS and iPadOS

One-finger accelerated scrolling now supported on every scrollable DOM element (iframes and elements with overflow: scroll) which makes the -webkit-overflow-scrolling style to promote momentum scrolling officially deprecated.

I'm not skilled enough to know what this means or why it would cause iScroll to no longer function. Is there any hope that iScroll can continue to function on this website, perhaps with some tweaking, or JavaScript overrides of some kind?

iScroll itself has not been updated since 2017, and I kind of doubt there are any plans for a patch. For now, I just have to figure out how to get this website working again.

Thank you!