The first error is:
A successful transaction has already been completed for this token.
The second one says:
Processor Decline 15005
The first one means they tried to do the same checkout twice and paypal recognized it and refused the second one after a successful one.
The second error means the credit card company or bank refused the payment.
Neither of these errors would result in repeat payments... they are clearly failed payments. The issue is how or why the user had more than one successful payments, not these failed ones.