It comes down to the distinction between self and other, and the moment that the shave begins.
In this scenario, the barber is both self and other depending on the circumstances. When the barber is both subject and object, the shave occurs in either outcome.
"Do you shave yourself? (Barber shaves) If not, come in and I'll shave you! (Barber shaves). I shave anyone who does not shave himself, and noone else (Barber shaves, as he did not shave himself until he started shaving)."
The conflict arises because we erroneously assume that when the barber becomes the object, someone else must be the subject. Why must this be true?
He remains unshaven up until the point when he (subject) decides to shave himself (object).
It is different aspects of self. To subject, and to experience in the same instance.