Setting up the situation:
1 - Customer creates bank funding source and initiates microDeposits to this bank account. (microDeposits in-flight)
2 - Customer finds out that he mistyped his bank account number. He edits the bank funding source to change the account number to be correct.
Based on this case, microDeposits will fail and the bank funding source will be removed.
This will be due to the in-flight microdeposits not being able to clear to the bank. Remember that the microDeposits already in-flight cannot find the correct bank account.
Because of this. you will receive an R03 return code and Dwolla will automatically remove the bank. Regardless of whether or not the Customer edited his bank funding source and initiated a new set of microdeposits, the funding source will be removed.
Best practices would state that your application will queue the Customer to start the full bank funding source adding and verification process over again.
To read more on transfer failures, feel free to check this article out.