The Angel of San Bernardino - S3-E20
Other mistake: Lucifer's obsession with Bones is highlighted here when he confronts someone as a killer only to realise it's because he's an actor who played a killer in the Bones episode Intern in the Incinerator (a role Scott Rinker did play in real life). Kevin Alejandro (Dan) and Aimee Garcia (Ella) also played roles in Bones, which Lucifer never comments on. In fact so did Jeremiah Birkett (Lee Garner, "Mr. Said Out Bitch").
Factual error: When we see Dan's computer while he's running the trace there are 4 results shown, but they're all the same: 256.256.256.256, an impossible IP address.
Audio problem: Lucifer is playing the piano at Lux, but he steps away from the piano about a second before the piano stops playing. (00:04:06)
Continuity mistake: When Maze says goodbye to Lucifer and takes off on her motorcycle, the cars around change. You can see 2 cars parked with a car next to it with its blinker on. Then there are 3 parked cars and the end one has its hatchback up. Then as she drives off, it's a van. In the next shot the van and hatchback are gone.
Is This Really How It's Going To End?! - S5-E15
Continuity mistake: When Dan hands Ella the phone number, he's holding it by pinching it on the bottom. In the next shot, he's holding it on the side.
Who's da New King of Hell? - S4-E10
Continuity mistake: When Lucifer, as the Devil, tells the demons to go home, all the bodies fall down. We see the bodies fall down behind Chloe, too. After the shot of the Devil, the camera goes back to Chloe and the bodies all fall down again.
The Sin Bin - S3-E10
Continuity mistake: The eyes Lucifer draws on The Sinnerman change at various times. Even later, when he darkens them out, they change as well.
Liar, Liar, Slutty Dress on Fire - S2-E2
Continuity mistake: When Lucifer gets the doll out of the box, the doll's box is either face up or face down depending on the shot. (00:24:30)
Liar, Liar, Slutty Dress on Fire - S2-E2
Continuity mistake: When Lucifer is examining the doll, the way he holds it changes between shots. In one shot, he is holding the packaging, and in others, he's holding the item. (00:24:20)
Everything's Coming Up Lucifer - S2-E1
Continuity mistake: When Chloe goes to ask Ella if she believes in God, Ella has her hands on or off the microscope depending on the shot. (00:32:20)
Everything's Coming Up Lucifer - S2-E1
Continuity mistake: When Lucifer walks out of the police station having worked out who Bobby B is, Chloe has nothing in her hands in one shot, and a piece of paper in the next. (00:30:40)
Everything's Coming Up Lucifer - S2-E1
Continuity mistake: When Lucifer and Ella are talking for the first time, Ella's hair changes from neat to messy between shots and back again. (00:08:50)
Everything's Coming Up Lucifer - S2-E1
Visible crew/equipment: When Lucifer and Chloe are walking across the set at the start, the camera rig is reflected in the car's paintwork. (00:05:20)
Continuity mistake: When Chloe turns the picture of the cufflink upside down to Dan, her grip on the photo changes between shots. In one, she has one finger behind the picture, but in the front angle, all of them are at the front. (00:33:10)
Continuity mistake: When Onyx opens the box, the way he holds the lid changes between shots. (00:19:50)
Continuity mistake: At the start, the man's hands change position around the woman during instant cuts. (00:01:40)
Continuity mistake: When Lucifer is walking towards the cowering Lindsay, she has her gun in her left hand. When the shot changes to behind Lucifer, the gun is now gone. (00:34:20)
Continuity mistake: When Lucifer hands Linda the leaflet in the carpark, the way he holds it changes between angles. In one shot he's holding the sides and in the next he's holding the top. (00:25:40)
Answer: Boo Normal and Once Upon a Time were going to be part of season 4, then the show got cancelled (before being picked up elsewhere). As such they were added on to the end of season three as "bonus" episodes, hence the continuity being off. But not really a mistake, just a quirk of broadcasting. Boo Normal was originally going to be between the episodes "High School Poppycock" and "Infernal Guinea Pig" in season 3 before being slated for season 4, presumably because aside from the point you've raised, it was fairly flexible, continuity-wise.
Jon Sandys ★