Two scenarios. Tables merge and there's empty seats between the dealer button and the small blind or big blind. The dealer button is supposed to jump to the person who paid the small blind. Instead it moves one seat over and forces the person who just paid the blind to pay it AGAIN. So the person pays the blind, table merges and pays the blind again. This error killed my stack in the tournament and the chance to go all in on the button in the next hand.

Another scenario if you get moved to a table and the blinds have been paid by the people around you. Then you have to wait a hand for the dealer button to pass you. Once the dealer button reaches the person to your left then you can be dealt cards.