Why are iPads causing checkout issues on my online store?

Does anyone else have a problem with ipads and their shopify checkouts? we are having to tell our customers to enlarge the cart and then scroll down to find the checkout button.

Also we are having issues with people having trouble using our store with their ipads. One customer has bought 6 times previously and latest one was 1 month ago and then the last 2 days she can’t purchase anything.

Any ideas as this keeps happening, shopify say its not them, website design team says it works on their ipads. but still have this issue.