Revealing mistake: When Pope bursts into the infirmary and sees Westmoreland's body, watch the collar of Westmoreland's jacket. You can see it moving up and down as though he's breathing. (00:03:30)
Revealing mistake: After Pope enters Scofield's cell to see the escape hole, we see him standing outside the cell looking out at everyone throwing toilet tissue etc. If you watch closely right after we see a guy pulling his pillows toward him to tear up, it cuts to another inmate who is throwing stuff out as well. Only thing is, we see the cell door slides to the side slightly which would indicate that the cell doors where not locked. In the event of an escape, lockdown would happen immediately, with all cell doors locked with the prisoners inside their cells. (00:04:00)
Answer: Because of coincidence.