Plot hole: There is no reason for the prison guards to use portable computers in full view of the inmates to input the sonic deadline code. The guards can walk outside of the deadline whenever they need to input the code, or radio the guard on the outside to lower and raise the deadline like they do when bringing the workers out. In fact, this plot hole is compounded by the presence of the guards stationed outside of the deadline with their own computer, which makes the guard inside the deadline completely unnecessary. The interior guard is only there so Weiss has a way to get both the code and a computer, but this prison set-up makes absolutely no sense.
Continuity mistake: When people are walking into the building before you see where Amber lives, she is wearing her white robe and watches the news report that Richards shot the people at the airport at 'point blank range'. She says, "But that's not true!" and you can see Richards walking into the building wearing his work clothes at the bottom left corner. That scene had already been seen when Richards went to find his brother Edward, who lived in Amber's room previously. (00:27:53)
Continuity mistake: When Buzzsaw runs by Richards, cutting the pipe in half, he has the chainsaw on his left hand. The camera watches Buzzsaw turn around, and you don't see the chainsaw, as the rider's left hand is on the handlebar, controlling the turn. The camera cuts to Richards for a second, then back, and the saw is on Buzzsaw's hand again.
Other mistake: The list of possible prisoners contestants the computer goes through shows different information, but the page with the 8 rows of double letters and numbers remains relatively the same, even though it's suppose to show variations and different information (i.e. AA always has -583 and -5483 and BB always has -484 and -4838).