Is there an option to undo a bank reconliation?

Yes, there is, Ccannon. You can ask your accountant for assistance in un-reconciling them one at a time, or you can do it yourself by going to the Chart of Accounts. I'll guide you how.

Option 1: Invite your accountant. They can undo the entire period at once using QuickBooks Online Accountant.

1. Go to the Gear icon in the upper-right corner and select Manage Users.
2. Go to the Accounting Firms tab.
3. Click the Invite button. Enter the accountant's information.
4. Click Save.
5. Let your accountant undo the entire reconciliation.

Option 2: Manually undo them one by one.

1. Go to the Bank transactions and select Chart of Accounts.
2. Find the account and select View Register. 
3. Review the check column. If the transaction is reconciled, you’ll see an R. Select the box and keep clicking it until it's blank. It removes the transaction from the reconciliation.
4. Select Save. Then close your register.

Additionally, check this article for tips about fixing reconciliation: Fix issues when reconciling accounts.

Click the Reply button if you have other concerns about reconciliation process. I'm here to help you around to help you anytime.