customerForOrder form error vanishes after filling the address form and user won't know why the proceed to payment button is still locked

[parkashay]

In the checkout page, There is a bug where, when the customer for order form (with email, firstname and lastname) is filled with a already registered email, first the error will show up as *you cannot use this email. But if the user scrolls below and starts filling the address form, by the time the address form is completed filling, the error that was above is gone due to the response of the address form replaces the error value from previous response. And the user won't have any idea why the 'proceed to payment' button is still locked even after filling all fields.
This issue is affecting mobile users as the user will scroll down as soon as the form is filled and by the time error pops up, it would not be in the viewport.