Visible crew/equipment: As Denzel walks into the lodge for the end scene and stops in the middle of the room, the camera rotates to the right and holds position. Now watch the first window at the right of Denzel, some shadow of the crew reflects on the glass and stops on the wall on the left of the window. (01:42:05)
Factual error: In the scene where Hobbes is talking to Reese in his cell, Reese talks to him in a foreign language. It's stated on at least two occasions that Reese is speaking Dutch. He isn't - he's speaking German.
Revealing mistake: When Hobbes is searching for information about Milano, he types his search into the webcrawler search engine and it takes him straight to the front page of the newspaper that is reporting on the events he is searching for. With the search terms he used there is no way he would get that result. You may argue that all the boring bits of websearching were cut, but for his second search he goes back to the web search instead of the newspaper's own search to get the next year's article. (00:22:00)
Audio problem: When Reese is in the chamber waiting to be gassed and singing "Time is on my side", the reflection in the glass shows him sitting totally stone-faced. His lips aren't moving at all.
Continuity mistake: When Hobbs (D. Washington) enters his brother Art's bedroom, soon to find him dead, he opens the door without closing it. After grieving for a short time he stands at the door, now closed, as he gathers himself as to what he just saw.
Suggested correction: You can hear the door close by itself as soon as he enters the room.