Favorite Son - S1-E6
Visible crew/equipment: When Linda and Lucifer are having a discussion at the end, a light screen is reflected in Linda's glasses. (00:39:10)
Visible crew/equipment: After the brief discussion in the hallway outside Linda's office, as Lucifer walks off a green screen is reflected in her glasses. (00:11:50)
Revealing mistake: When Lucifer convinces Ricky not to jump off the building, it is blatantly obvious that the two actors are on a green screen and not an actual rooftop. The green glow around their heads is visible. (00:13:10)
Visible crew/equipment: When Lucifer jokingly says to Ricky that there's "nowhere to go but up", part of the crew/equipment is reflected in Ricky's glasses. (00:15:00)
Continuity mistake: When Malcolm lifts his jacket to show he is unarmed his jacket position changes between the two shots. In the first shot his jacket is hanging low and in the second it's held high. (00:19:40)
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)
A Priest Walks Into a Bar - S1-E9
Visible crew/equipment: When Linda is talking to Lucifer a white screen is reflected in her glasses. This can't be the window as the window is behind her. (00:03:30)
A Priest Walks Into a Bar - S1-E9
Continuity mistake: When talking to the priest in Lux, Lucifer's hands are constantly changing positions between cuts. (00:24:20)
A Priest Walks Into a Bar - S1-E9
Continuity mistake: When Lucifer goes to speak to the priest on the balcony after finding out about Connor Lucifer has his right arm by his side as he walks out. When the shot changes to outside his right arm is bent at the elbow and in front of him. (00:28:30)
A Priest Walks Into a Bar - S1-E9
Continuity mistake: The position of the priest after he has died changes between when Lucifer walks over to the other person and when Connor walks over to the priest. (00:35:00)
A Priest Walks Into a Bar - S1-E9
Continuity mistake: At the end on the balcony Lucifer's cigarette switches hands between some instant cuts. (00:36:30)
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 ★