Opened a support ticket for this a couple of days ago and haven't heard back so figured I'd try my luck with the forums. Since it's a consistently reproducible issue, and 10.3.3 is the most current version of iOS, I imagine it may be happening for a lot of people.

When people go to our store on the mobile app and add items to their cart, they disappear as soon as you click anywhere else on the site. If they click to another one of our pages, the cart simply zeroes out. If they have items in their cart and try to click "Checkout," they get an error message that says "there's nothing in your cart."

I managed to find a friend with an iPhone running 10.3.3 who could consistently reproduce the issue. The site works fine on Chrome on iOS.

The Safari version where this is happening (from whatsmyuseragent.com) is "Version/10.0 Mobile/14G60 Safari". Has anyone else encountered something like this? Is there some change we could make to our site or store settings to get rid of it?