In the diner where Ray brought his son Will they receive their order overly quickly It couldn't even have been able to start being made in that short of time. Also when she brings them their plates, with Ray's order she says it's a burger with no onions when you heard him asking for it he just asked for a cheeseburger he never made extra specifications incidentally when you see it it does have cheese on it. When Ray goes to put ketchup on it you see him with the bottle in his left hand and almost about to pop the cap with his left and the next shot from the back you you hear the pop of it opening but it ends up emerging from the right side like he was doing it the exact opposite way, switched hands incongruently. When shot back from the front his plate is turned 180 degrees on the table and he's holding the top bun randomly in his left hand when it already been taken off previously.
When Ray beats up Finn in the bathroom of the diner it hardly looks like Ray punches him with any much force under his arm. And when it shows the outside of the door he only may have had time for a couple more punches at the most. Later when he goes to see Keegan at his place Finn opens the door with a huge Red mark around his eye and mouth which I don't find he could have inflicted that damage with what happened it looked unbelievable.
When Keegan dies, the barbell is diagonal over part of his throat. Next, it is parallel to the floor and across Keegan's whole throat.
Shortly after being told to "have a nice flight", the main characters are seen beginning to cross a sky-bridge that rather clearly shows them heading towards a parking garage.
Ray's head wound was sloppily stitched by his father but there was no sign of this for the rest of the film.
Much is made of the Travolta character carefully selecting the perfect antique frame, mixing his own pigments using raw minerals, etc.. None of this has any effect on the plot. Travolta admits he will not create an exact copy, and regardless, the forgery is never inspected.
When Ray is explaining to Will why new oil paints cannot be used to forge an old painting, he correctly mentions that a big reason is because air pollution from the 20th Century causes tiny little black specks to be trapped in the new paints. However, he does not mention one very important reason: any oil painting made before the first atomic bomb, which was detonated in 1945 at the Trinity test site in New Mexico, would not have trapped any of the elemental and sub-atomic particles that were thrown into the atmosphere by that or later blasts. This is a key test which can be done to determine positively if a painting was made before or after the first atomic bomb. Also, this is a very expensive test.
When Ray and Will meet in Will's bedroom the boom mic shadow is visible two times. First, on the wall above the guys when they were talking, and then the shadows are above the door when Ray is leaving the room,.
John Travolta's character Raymond Cutter is supposed to have a Boston accent which isn't very believable when he does it and he also goes in and out of it through the movie.