Red Light, Green Light - S7-E4
Other mistake: The crash at the start is staged - the semi truck is driving at 20/30mph, is T-boned by the van, and stops instantly. No screech of brakes, no allowance for the driver's reaction time. In the shot of the impact it's moving at barely walking pace, hence being able to stop so quickly.
On the Scent - S7-E9
Continuity mistake: Sherlock and Marcus visit a suspect's house. There are a bunch of cell phones on a console. One is gold with the name "'Mandy" on it. In a wide angle shot the gold phone is by itself next to some other black phones. Next closeup shot you see the gold phone is on a different position behind some other phones, and a green phone is added to the bunch. (00:18:40)
Unfriended - S7-E11
Character mistake: Odin Reichenbach talks to Sherlock about "doing the irrevocable", but pronounces it "irrevOWEcable." It should be pronounced "irrevacable" in both British and American English. He's supposed to be a highly intelligent, highly educated person - not a mistake he should make.
Suggested correction: Not necessarily. A lot of people have strange vocal tics where they pronounce a certain word in a certain way, usually without even realizing it. My grandfather was a smart guy, and he always mis-pronounced "toilet" as "ter-let."
Character mistake: Sherlock tells Odin at the bridge where he framed him for his own murder that they are opposite poles of a magnet - they repel. That's wrong - opposite poles attract each other.