When Calvin first logs onto the website and finds out its an auction finishing in 14 hours time, it is approximately 11pm so that would mean the auction would finish at 1pm the next day, but it doesn't seem to finish for at least 24 hours if not 36 hours.
When Bob and Calvin leave the bar, the bouncer requests the patron walking up to the door for their ID (using hand gestures). In the next shot further away from the door, we see the same patron and hand gestures.
When they are flying the plane, Bob intentionally shuts the plane off to simulate the plane going down. When he turns it back on they show him flipping the master switch back on. In GA aircraft this switch only controls the electronic systems (which are still operative) of the plane (navigation, radios) and has nothing to do with the engine of the plane, which is either shutoff my the mixture, fuel shutoff or magneto switch.
Bob rigs up the sprinkler head to go off in Calvin's office and, a few minutes later, all the sprinklers on the office floor activate. In reality, only the one sprinkler head will activate. It will not cause all of them to go off.
During the fight scene over the bridge, Stone gets shot. Later that same evening at the homecoming, you catch a brief glimpse of the region where he was shot. There is no bandage covering the area and there is no sign of a wound.
The goof item below may give away important plot points.
Just after Bob is announced as the reunion homecoming king, two men cross behind Bob and Calvin. A few lines later, there is a different camera angle focusing on Calvin and the same two men cross again from the same direction. During their first cross, there is also a cut-away to a crowd shot. The same man in the blue shirt that is crossing behind them in the close-up shot is also standing in the back right of the crowd shot.