How many wires are coming out of that little black box? What color are they? This will help yuy determine just what that little black box is.
If it has three wires, one each of brown, brown/white and green/yellow it's the turn signal flasher. If it is then it's probably bad. Just replace it with most any two prong flasher from the parts store. Just plug the two prongs into the brown and brown/white wires in the socket.
If it has five wires, one each of red/yellow, brown, black, green/white, green/yellow, it's the turn signal canceler, If so, it's bad, just remove it.
Either of these options will disable the self canceler. You will need to turn the signals off your self.
Leo