In the case of U.S. securities options, the OCC will automatically exercise option contracts at expiration only if the option is in-the-money by $0.01 or greater.
As a result, account holders maintaining a call (put) spread with the short leg having a lower (higher) strike price that the long are subject to delivery risk if the short leg is in-the-money by $0.01 or greater and the long leg is not.