Continuity mistake: In the scene at the bar with Gideon when the black guy pours Gideon a drink it is only about 1/3 full. When Gideon drinks it in the next shot it is almost full.
Continuity mistake: In the scene where Brandon walks in on Top Dollar's meeting and there's a big shoot out, the guy in the trousers with hearts on them gets shot and killed, but a few seconds later you see him again shooting at Eric.
Continuity mistake: In the scene where Eric kidnaps T-Bird and forces him to drive the hot-rod to the dock, Eric holds a large silver revolver up to T-Bird's head, then removes a black automatic from T-Bird's hand and drops it into the front floorboard. A few moments into the chase we see Eric holding the black automatic to the side of T-Bird's head, and the silver revolver is gone.
Visible crew/equipment: When Lee shoots Fun Boy, Fun Boy falls backwards on to the bed. His leg flies up, and you can clearly see the cord coming from his pants that is attached to the fake blood bag. (00:39:05)
Revealing mistake: When Draven sends T-bird to his death in his car, the real Ford Thunderbird is replaced by a fake mockup using a flimsy one-piece fiberglass body mounted on a pair of straight axles. When it explodes, the body lifts off in one piece, warping wildly while the front axle simply falls away. No proper car components like engine, transmission, suspension and so on, are seen anywhere, though they should be. (00:57:05)
Audio problem: There is a scene where Eric is following the crow through a dark room. The camera trails off to show the crow's shadow and there is a sound as of wings fluttering yet the shadow is perfectly still. (00:10:10)
Continuity mistake: When Lee takes T-Bird in his car and the chase with the Police begins, the camera flashes to look at the chase through the eyes of the crow, the Police cars emergency lights are strobes, but when the camera reverts back to the chase scene they are the old style rotating flashers.
Deliberate mistake: When the crow drops Shelley's ring into Sarah's hand at the end of the film, the sound of metal upon metal is heard. (01:30:00)
Plot hole: Eric and Shelly were killed because they were trying to fight tenant eviction. Yet, a year later the building is seemingly abandoned. Eric and Shelly's stuff is even still there. So what were they killed for if nothing was ever done with the building?
Other mistake: The crow leads Eric along a rooftop at the start in the pouring rain and down into a building. However, as Eric is walking into the building there are no wet marks from his soaking wet boots. (00:10:00)
Continuity mistake: When Funboy gets shot in the leg it hits his right, he is then shown clutching his bloody left leg and then his right when he is dragged into the bathroom. It goes back and forth like this. (00:38:20)
Continuity mistake: Watch T Bird's facial scars, they change from small to big throughout the police chase.
Continuity mistake: When Eric is about to leave Gideon, he points the shotgun at him, then holds it vertically. Just after he says "your job is to tell the rest of them..." we see a shot of Gideon, and the barrel of the shotgun is visible in the top left corner, pointing at him again. Back to Eric, and the shotgun's still vertical. (00:30:00)
Continuity mistake: When Sarah is sitting at the Hot Dog stand near the beginning of the movie, her hood changes from being up and down without her touching it.
Continuity mistake: After Eric spreads petrol (or something ignitable), he leaves Gideon's Pawn Shop with the shotgun full of rings. When standing outside, he shoots the shotgun into the building. First of all, I doubt that even petrol could make such a big explosion. Secondly, if you watch closely, the top of the building seems to blow up before the bottom. (00:31:05)
Visible crew/equipment: When Eric disappears for the first time the camera spins around on Albrecht. In this shot, the shadow of the camera can be seen at his feet. (00:31:50)
Continuity mistake: When officer Albrecht shows the Shelly Webster file to Eric before the "nothing is trivial" conversation, the police hat changes position over the table in every shot. (00:44:30)
Continuity mistake: When Darla prepares breakfast for Sarah, the bottle of juice on the table changes positions between the shots. (00:58:50)
Audio problem: When Albrecht asks to Eric if he is going to vanish into thin air again, the shot changes and Albrecht still is moving his mouth but now he is voiceless. (00:46:30)
Continuity mistake: When Eric reaches forward to touch Top Dollar's face to show him Shelley's thirty hours of suffering, he reaches up with his right hand, but in the next shot, his left hand is on Top Dollar's face followed by his right hand. (01:29:45)
Answer: There is no explaination given in the films, they are just brought back when the crow feels it is the right time to avenge their murder.