It has been mentioned by a few Timber customers that transactions with either a CVV or AVS mismatch were authorized.

Most commonly, what is happening is that the Cardholders' bank approved the transaction, despite the fact that there was an AVS/CVV mismatch. Then, Verifone permitted the authorization to come through as "Approved". --This indicates that your Verifone account is set up to permit that authorization, even though AVS verification failed.

It would be a good idea to review your Verifone account settings to ensure that both AVS and CVV mismatches will result in a Declined message.