Bank Reconciliation Out of Balance

I reconciled on 4/30/18 and all was good.  Then i realized a bank transfer was entered twice, so i entered a transaction going the opposite way to clear one of them out.  When i reconcile the statement for 5/3 and select both of the transactions it shows it is out of balance by one of the transactions.  I have also noticed that the book balance does not reconcile to the G/L balance by this same amount.  What can cause this to happen, and how do I fix it?