Cersei states that there are only two lion pendants in the world, hers and Myrcella's; actually, Joffrey gave Sansa an identical pendant in A Golden Crown (2011), and Tyrion gave one to Ros in The Wolf and the Lion (2011).
Brienne tells Sansa "Before your mother's death, I was her sworn sword. I gave my word I will find you and protect you." That was not the oath Brienne swore: in Dark Wings, Dark Words (2013) she said her oath was to exchange Jaime for the Stark girls and bring them back to Catelyn.
At 46:50 (DVD Release) you see Missandei in a group walking up a set of three steps. At 46:59 she lifts her skirt to clear the top step. Cut to two Mereneese. At 47:03 you see her lifting her skirt up again, even though she should be well on the flat surface of the platform by now.
There is an aerial shot of the ship that Arya is sailing on when she is arriving into Braavos. There is a great deal of wake behind the ship as if it is sailing at a high rate of speed, yet the sails are parallel to the direction of the ships heading. They would have to be perpendicular to generate the speed that is being portrayed.
At the end of the final credits, the word "Spanish" is misspelled "Spainish."
During the vote for who will be the new Lord Commander of the Night's Watch, Jon appears to be tied with Ser Alliser until Maester Aemon gives Jon the winning vote. However, counting the tokens reveals Jon has 30 votes to Alliser's 28, before Aemon casts his vote.
More than once, wide shots of the gathered people of Meereen show them standing motionless while the audio has them shouting in great commotion.
It makes no sense why the Sand Snakes forewarned Cersei that they intended to harm Myrcella.
While reciting her death list, Arya does not mention Ilyn Payne.