Rules

16. When Players Change Ends
The players shall change ends at the end of the first, third and every subsequent alternate game of each set, and at the end of each set unless the total number of games in such set is even, in which case the change is not made until the end of the first game of the next set.

If a mistake is made and the correct sequence is not followed the players must take up their correct station as soon as the discovery is made and follow their original sequence.