Revealing mistake: Season 5, episode 8, "My Name is Mac Taylor": When the killer sets himself on fire, he's not wearing any gloves. In the next shot he is, to protect the stuntman from the flames.
Revealing mistake: On both occasions when Sandra is sitting in the boat going out on the lake to dive actress Amanda Redman has obviously been replaced by a stunt double.
Revealing mistake: When Denise is showing Brad how to kiss, the first kiss is a typical "stage kiss" with their lips pretty clamped shut, but she then details what he's doing wrong with his tongue, which clearly wasn't at all involved with the sort of kiss they just shared.
The Delivery - S7-E6
Revealing mistake: Eddie's bar has just burned down, and everything is ruined. However, the glasses above the bar are pristine and clean. At the very least, they'd be blackened and smeared by the smoke and soot, even if the heat of the fire hadn't destroyed them. (00:10:28)