Hazrat Masruq (may Allah have mercy on him) says that a slave may be returned because of baldness.

It is narrated from Hazrat Sha’bi (may Allah have mercy on him) that a man bought a slave from another man. When he took him away, he found that the slave was bald. The man, disputing with the seller, came to Hazrat Shurayh (may Allah have mercy on him) and said,“I bought this slave from him, but he is bald. Please look at his baldness; this baldness is not something new.”Hazrat Shurayh (may Allah have mercy on him) said,“I cannot both judge and be a witness. Show him to some other people besides me, then come to me with them so that they may testify in your favor. Otherwise, the seller will have to swear an oath that he did not sell him with baldness.”