Continuity mistake: When Tru and Harrison talk on the phone near the beginning of the day's second incarnation, it is pouring rain where Harrison is, and he's standing under an awning. It's not raining by Tru - or at least not enough to be noticed by the camera or to get her wet, which isn't a problem in and of itself, except that everybody around Tru is carrying umbrellas for some reason.
Plot hole: The first time the day happens, Tru tells Luc that Mark called her, and later she tells him that he wants to talk to her, and Luc is fine with that because he trusts her. The second time, knowing that Mark was killed, she decides that she should agree to meet him when he first calls. But she lies to Luc about what she's doing. Why? She knows that he wouldn't have a problem with what she's doing, but instead she tells a lie that conveniently drives the episode's romantic plot.
Plot hole: There doesn't seem to be enough information about Mark's stabbing for Davis' computer program to determine how tall the attacker was. The main thing that's missing is any information about the angle of the knife's penetration. Without that, there should be no way to obtain the killer's height.
Plot hole: When Tru realizes that the yellow-handled knife Lindsay bought was the murder weapon, she gets rid of it. As a result, Lindsay needs to borrow a knife from Tru's neighbor so she can slice vegetables. The fact that Lindsay bought a knife for Tru, combined with the fact that Lindsay couldn't find one later, implies that Tru doesn't have a suitable knife of her own. But Tru served cut fruit to Harrison and his date several episodes ago, so she must already have a knife like that. In fact, pretty much everybody does. And there's no indication that Tru went around hiding all of her knives. In fact, the episode focused on that one, yellow-handled knife to an overly dramatic extent that bordered on inadvertant comedy.