The one-eyed bartender is clearly missing the right eye but when he turns to his left and we see the right side of his face his right eye is open then when he turns back at the girls, his right eye is gone again.
When Gru and Dru hook onto the side of the cliff the hook doesn't hook at the top and when they drove over top and landed that wouldn't have been possible because the hook didn't reach the top and couldn't pull them to the top.
At the beginning when Balthazar Bratt does his diamond heist, the AVL obtain incorrect coordinates of his location. His heist took place on the coast of Hollywood, however on an online map the coordinates show that he was in Tennessee.
In an early scene Clive the Robot ejects a cassette tape and spins it and inserts it to play the other side, which would put the open tape end on the wrong side of the tape deck. It needs to be spun around as well to keep the open tape end on the correct side of the deck.
During Gru and Dru's heist, Dru is climbing up the exterior walls of Bratt's lair with his special suit set on "Sticky" mode. He then has to switch to "Camouflage" when spotted by security systems. If he switched suit modes, then "Sticky" would have turned off, thus causing Dru to fall.