Having known the FBI are going to raid the office why would Seth go to Chris to ask him to sign a sell ticket so Harry Reynard could "dump" his shares on the open market and make his money back. Seth confirms this goof by saying "what's the difference?" The FBI would cancel all transactions made long before the raid.
When Greg gives Seth his first orientation meeting he tells him each potential client card has only their name occupation, and phone number, however when Seth attempts to pitch Harry Reynard he asks him what he does for a living.
When Seth is driving on the Long Island Expressway he says he goes to his interview off exit 53. In the next frame you see Seth driving on Northern Blvd. which is exit 32. Further in this scene we see Seth driving on Northern Blvd. east but then cuts to a scene where he is traveling west on Northern Blvd. which would make him driving the total opposite way of where he wanted to go.
When the FBI arrests Seth, they tell him to go to work the next day and copy his C Drive onto a floppy. This would be impossible as a floppy disc only holds 1.5 megabytes and his hard drive would hold Gigabytes, at least.
After Seth and Chris have their argument in the stairwell right off of the boiler room, Seth goes down at least one flight of stairs on his way out. In the next scene he passes Abby in the receptionist area that is on the same floor as the boiler room - because he's been bumped upstairs to nicer offices.
When Seth's father calls him to say that he would go in with him with the IPO scam he states first that "I'll make sure you won't get caught" and then "I have a friend..." While the FBI playback is different, since this wasn't court testimony, they may have been using an altered tape.