Stripe Authorises payment before form validation causing problems
Lot's of improvements have been made in 6.3.2 and (not yet released) 6.4. But we still need to do a lot more to make this work reliably.
Seems like this might be an issue. Please close immediately if it is intended behaviour. https://civicrm.stackexchange.com/questions/34012/stripe-authorises-payment-before-form-validation-causing-problems