Can half an outlet go bad?

Yes, it is entirely possible for only half of a duplex wall outlet to go bad while the other half continues to function normally, a malfunction typically caused by a broken internal contact spring or a split-circuit wiring configuration. In many residential installations, duplex outlets are wired as split-circuits where the small brass break-off tab connecting the top and bottom hot terminal screws is removed so each half can be controlled independently. Alternatively, physical wear can break an internal spring contact inside one half. You can troubleshoot split circuits safely by isolating power at the circuit breaker. You can verify that your corrective action is successful when removing the wall plate, checking the brass tab, and replacing a damaged receptacle restores full power.