Before you just automatically start to calculate interest for failing to escheat funds on a timely basis, you may want to review your customer's history with your bank to see if they had some form of contact with your bank during the dormancy period which, under WA law, would have taken the CD out of dormancy status.
I dealt with a similar situation for a CA bank many years ago. Under CA law, a customer's activity on any account will apply to all of their accounts. By going through the customer's entire relationship with the bank and all activity on other bank accounts (e.g., non-automatic deposits into and withdrawals from other accounts, providing a POA, changing privacy selections, adding a POD beneficiary), we were able to determine that nearly all of the so-called dormant CDs would not have been escheated. You should consult with your bank counsel to determine if this approach might help you.