You note that the bank should not be accepting checks payable to a business for deposit to a UTMA account. Obviously, that is foolish and it is the root cause of your problem. Allowing those items to be deposited makes your bank complicit in the custodian's use of this account in attempt to defraud creditors and perhaps the beneficiary.
You do not say what methods can be used to access the account in addition to the debit card. I suggest you send the custodian a letter asking the customer to close the account, indicate that all future withdrawals must be in person and, that if the account is not closed by X date, your bank will close it unilaterally. Your check would be payable the way the account is titled, not to the custodian and not to the beneficiary. Your explanation need not be elaborate and you might be wise to just say it's because the child has reached the age where delivery is required by the statute.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.