Further research showed that older rejections (some more than 6 months old) were in the system, and even though charges were paid subsequent to that rejection, the next rejection forced the Payment Method to CK. This is because rejections are cumulative, regardless of time.
The following query will display all the Transaction records that fall into this category (where they were rejected beyond 30 days in the past):
SELECT T0.* FROM TRANSACTIONS T0
WHERE T0.ACCOUNT_ID IN (SELECT ACCOUNT_ID
WHERE STS = 'A')
AND T0.TRANSACTION_TYPE = 'PL'
AND T0.GIFT_KIND = 'SG'
AND T0.PAYMENT_METHOD = 'CK'
AND T0.BANK_REJECTION_COUNT = 2 -- Remember to use your system's CP rejection count here
AND EXISTS (SELECT 'X'
FROM TRANSACTIONS T1
WHERE T1.ACCOUNT_ID = T0.ACCOUNT_ID
AND T1.PLEDGE_NUMBER = T0.PLEDGE_NUMBER
AND T1.BANK_REJECTION_COUNT = 1
AND T1.PROCESSED_DATE < T0.PROCESSED_DATE - 30)
ORDER BY T0.GIFT_DATE DESC, T0.ACCOUNT_ID, T0.GIFT_SEQ DESC, T0.ADJUSTMENT_SEQ DESC;