My Cloudformation stack is created with above error and its status is ROLLBACK_COMPLETE.

After my investigation, I notice that at times what happens is that the mapping will still remain even though the stack is deleted. Easiest way to get around it would be to use AWS CLI and delete the mapping.

I delete the event source mapping with UUID mentioned in error message by running “aws lambda delete-event-source-mapping –uuid dc07eb6b-b360-4f6c-9e41-1eb1835cc678”. And I verified that event source is deleted by running “aws lambda list-event-source-mappings –function-name <my_function>”.

Once the Event source mappings were deleted I am successfully able to create the stack without any issue.