Thanks for keeping us posted, bloom1.

Let me give updates about the current investigation about the issue with duplicate transactions from Chase Bank.

I've researched the status of the investigation about duplicate transactions with Chase Bank and found out that our engineers are still working with your bank to come up with a permanent fix. 

Meanwhile, I can help you match your Chase Bank balance and QuickBooks balance. There are several reasons why your balances doesn't match, among these are the following:

• Outstanding transactions
• New transactions for a connected account
• Duplicate transactions
• Edited or deleted transactions
• Credit card (liability) account

I've added an article for more information fixing incorrect balances in QuickBooks Online (QBO): How to fix differences between QuickBooks balance and bank balance.

Should you have additional questions about handling duplicate transactions and fixing bank balances, don't hesitate to ask me here in the Community.