The distance between Mortimer and Holmes in Holmes's place when Mortimer is greeted at the door changes changes in consecutive shots.
It is impossible to completely sink in quicksand. If a person ever gets caught in quicksand, the furthest they would sink is up to their waist.
When Baskerville and the others arrive on the moor, discussing Grimpen Mire, a plane can be seen flying in the distance.
The letter addressed to Holmes reads 121b Baker Street not 221b.
At 29min of the movie, when they travel in the moor to arrive to the house of Baskervilles, you can see a small aircraft, kind of Cessna, far away in the sky, moving from left to right. It's tiny but clearly visible.
When Watson and Sir Henry arrive at Baskerville Hall and Watson and Holmes leave the place, the surface of the driveway to Baskerville Hall is made of tarmac or asphalt.
At 21:55 the boom person can be seen clearly on the left side of the screen wearing blue jeans, a brown belt and a white t-shirt with his elbow up in the air.
In the scene where Lestrade believes he's captured Laura Lyons' killer, Holmes quotes from Scripture: "Love is as strong as death, jealousy as cruel as the grave." He and Lestrade both agree that it's from Isaiah 6:8. It's not. It's from Song of Songs 8:6., and the actual quote is "Love is strong as death, jealousy is cruel as the grave."