Factual error: Walt's medical records contain an error - on the left side of the folder, his address is listed as "Detroit, CA" and it's correctly listed as "Detroit, MI" on the right side, although as pointed out in another entry, the house number is completely wrong in the medical records.
Character mistake: The information on Walter's "patient information sheet" lists his address as 5962 Delco St but numerous shots indicate his house number is 238. (01:03:25)
Continuity mistake: When Tau is working under the rain, Walt is staring at him over his house. It's pouring heavily, but on the reflection of the window just behind him you can see the bluest sky.
Continuity mistake: Near the end of the scene where Walt scares the Asian gangsters away from his lawn, when they are running away to their car, there's a shot behind Walt where he's seen putting down his rifle. However, immediately after that, Walt is shown from the front, still holding up his rifle and pointing at the Asians.
Continuity mistake: Near the end of the movie, Tau comes over to Walt 's house at 4pm. After locking Tau up in the room and leaving it is broad daylight. However, by the time Walt gets over to the gang banger's apartment it is pitch dark. Couldn't have taken more than 60 minutes to get there even with stopping to call Tau's sister. Detroit is in Eastern time so it doesn't get pitch dark until at least 7pm, later in daylight savings time, which is probably what time of year it was since it was obviously warm weather.