Addressing Multiple Unsuccessful Purchase Attempts

Person created an account, added one item to their cart and then submitted over 1000 purchase authorizations requests through Braintree using the same Mastercard.

Braintree handled it just fine and our server did not even seem to notice. :)

BUT, the account had an invalid email address and all failed transactions generated emails that also failed.

I have recaptcha v3 turned on for every possible step.

Is there an add-on or setting that can block multiple purchase requests like described?

Wondered if I might be risking my merchant account if this happened a lot?