Continuity mistake: In the shower scene the shower is turned off but you can still hear it running. Then it switches back on. You can see it off and on during same scene but the sound is always running. (00:50:00)
Revealing mistake: After Bennett takes off, Luther jumps on the edge of the prison. When he hits it, you can see the seemingly solid concrete edge wobble.
Continuity mistake: When Alice is shining her flashlight into the tunnel, note that the shower column is on the right side of the tunnel entrance. In the shots on the outside of the tunnel, that same column is on the left side of the entrance. (01:04:30)