I have searched the boards for this error and found that supposed Shopify have fixed it however I am still having customers get this error when they checkout.
Hi there Lisa,
Are you a plus customer?
Do you have any apps installed that add any features to the checkout?
Can you replicate the problem?
Do you have a screenshot? 
Cheers,
Gary
Hi Gary,
I’m a basic customer. No apps that add features to the checkout. I do have Afterpay and Laybuy however nothing new/changed.
I have been unable to replicate the problem and have been getting orders although not as many as usual hence wondering about the issue.