I agree with the others who stated just cancel it and block buyer. You're better off that way, because other wise people like this might leave you undeserved bad feedback and it's not worth it. If it's priced right you'll still sell it to someone else. I've given parts away when I discovered a slight problem with something after someone purchased something, and I was boxing. Very MINOR cosmetic issue, but I'm always wanting to error on the side of customer service and receiving good feedback.