When Richie Furst is running away for agent Shavers, into the abandoned building, the sweat on the back of his shirt changes size between the shots.
When Ritchie walks on the boat Ivan is chopping a fish with a glove on his left hand. When he shakes hands the glove is gone.
The bran cereal box changes postilions multiple times. First it is on his lap then it shows him setting it on the table and moving his hands away and the next scene shows him holding again.
When Ben Affleck's character talks about all the things he cannot do in the US anymore, he mentions Pittsburgh and its famous Primanti brothers restaurant chain, notably the specialty sandwiches they make. He pronounces it Pri-MAHN-ti, with the AN letters sounding like 'on'. Any big fan of the restaurant chain would know the proper pronunciation is Prim-AN-ti, with the AN sound similar to the name "Ann".
When Richie Furst is playing online poker to make his tuition there are several shots showing that he is actually playing on a Play Money Table - meaning no real money is being wagered.