The answer should be "when side-slip towards the left"
Reason- When a/c side slips to the left, more pressure/airflow is experienced on the left side and less on the starboard side.
Now since the left static port is non-functional, it doesn't matter how much the pressure it is experiencing.
However the right static port is functional and being shielded from the airflow, it experiences less ambient pressure and hence the capsule inside the case will be subjected to lesser compression and thus it will over-read i.e. will show higher than actual altitude.