Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: At the beginning, the preacher is walking around with the donation mug. The first kid to put a few bucks in does it across two shots and has a very notable yellow hand-held device when he puts the money in that was not there in the first shot. (00:02:00)
Lucifer, Stay. Good Devil. - S1-E2
Continuity mistake: The quantity of blood on the door changes between shots, incoherently, when Jimmy is hurting himself, smashing his head on it. (00:42:35)
Continuity mistake: During the scene in the school corridor with Lucifer sitting down and talking to Chloe's daughter, the same extras keep doing erratic back-and-forth for no reason (for instance the girl with a white jacket and pink shoulder bag) or just plain wrong (the kid with the horizontal striped maroon sweater who walks twice past Lucifer early in the convo). (00:24:50 - 00:25:50)
Quintessential Deckerstar - S3-E23
Continuity mistake: When Espinosa opens the waffle maker, initially he's holding it facing up, slightly away from him, then the shot cuts and he's holding it close to his body, facing outwards. (00:21:20)
The Would-Be Prince of Darkness - S1-E3
Continuity mistake: Lucifer gets waken up after his very PG foursome by Ty. When he says "Can you just help me, please?" Lucifer does not have his right hand on the shoulder of the girl, in contrast with the earlier and following take. (00:06:15)
The Good, the Bad, and the Crispy - S2-E18
Continuity mistake: When Lucifer is sending his mum to her new world, he is standing for the whole scene. They show a shot of Charlotte collapsed on the beach, and in the same shot, you see Lucifer on his knees in the sand. The very next shot, he is standing again. You only ever see him fallen on his knees when time starts back up again and the detectives realise where they are, which is a bit later. (00:37:25)
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 Lucifer helps Amenadiel, who has been stabbed with one of Mazikeen's daggers, Lucifer has one hand on Amenadiel and one by the dagger. The camera cuts, and now he has both hands on Amenadiel. (00:21:45)
Continuity mistake: When Linda asks Amenadiel if he is a real doctor, he has both hands raised. Camera cuts and now he only has one raised. (00:08:20)
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)
St. Lucifer - S1-E11
Continuity mistake: The way Malcolm holds the gun when showing it to Dan changes between shots. Note his grip. (00:06:30)
St. Lucifer - S1-E11
Continuity mistake: Just after saying the widow could hold the charity event at Lux, Lucifer has his hands clasped. As the camera changes angle changes however his hands are apart. (00:07:30)
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 ★