Continuity mistake: There's a clear mix-up in editing during the car chase. Marta checks her phone twice for Blanc's calls as she tries to get away from the police. The first time the phone signals 9:36 AM, the second time 9:34 AM. (01:31:50)
Continuity mistake: Benoit Blanc caught Marta eavesdropping through the stained glass and is doing now "some pokin'." She answers his questions with her arms straight, and listens to him with her arms folded. (00:23:40)
Continuity mistake: When Fran first takes the breakfast tray up the stairs, the mug of coffee on the tray is brimming. When she discovers Mr. Thrombey dead, the mug is mostly empty. (00:01:30 - 00:02:11)
Continuity mistake: The lawyer arrives at the mansion and gives the reading of the will at roughly 10:30 am (it's morning, he says he'll be ready "in 10 minutes" and a few minutes after you can see on the phone Jamie Lee Curtis' character holds in hand that it's 10:16). Marta gets immediately stormed by the angry mob of scorned relatives and escapes with Ransom, who drives her to a little roadside inn. It's not implied that they drove hours, but let's just assume it's noon or even past noon (which already seems a lot). Ransom feeds her beans, and Marta is forced by her odd gag reflex to spill the metaphorical ones. When she has just finished telling him how the "suicide" went... it's pitch dark outside, and at the mansion. (01:02:30)
Continuity mistake: After walking in the muddy path, Marta is greeted by very affectionate dogs. Daniel Craig approaches the dogs and the kneeling Ana de Armas with just his left hand in his pocket. Close-up, and he has both hands in his pockets all of a sudden. Return to the first wider angle and Craig's right hand is out of the pocket just as before. (00:58:10)
Continuity mistake: When Marta Cabrera and Ransom Drysdale are at the diner the first four times she has three beers in front of her. The fifth cut to her there are four beers in front of her. The sixth cut to her there are three beers again. (01:18:03 - 01:18:27)
Continuity mistake: During the denouement Marta asks "So why did she send it to me?", and Benoit Blanc replies with his right hand in mid-air - but it's in his pocket at the beginning of the next shot. (01:54:30)
Continuity mistake: Marta recalls in her head the facts of the fateful night during Blanc's coin flip. Harlan sits down in the attic room and grabs the Go pieces from the bag. He places the bag on the table when she tells him to take the "goddamn medicine and go to bed", but it is back in his lap at the cut, and on the table again at the next cut, midsentence. (00:32:50)
Continuity mistake: When Marta second guesses what she has been doing and holds both vials in her hands, when the camera cuts to Christopher Plummer one vial is still on the table. (00:36:30)
Continuity mistake: Walking outside of the shack with the recording equipment, Marta is rubbing the tape with the magnet. Notice the position of her hand when she is walking - correctly, she is holding the magnet end against the cassette. The close-up that reveals the trick to the audience though, starts with her holding it the opposite way. (There is technically time for her to flip it around in her hand in the couple seconds when her hand is not on camera, but we see her put her hand by her side to conceal the magnet's presence, and then how she holds it tightly against the same spot on the coat; switching the side the magnet is facing would require a deliberate movement with no sense or purpose). (00:57:00)
Continuity mistake: The quantity of barf on the killer's face varies between shots - in particular they have a big reddish bit on a cheek that disappears in the dramatic slo-mo side view when they push Marta down, weapon in hand. (02:00:00)
Continuity mistake: As the camera is panned wide with an aerial view of the estate there are no leaves on any of the trees. But as Marta steps out of her car, the trees are full of very colorful leaves.
Continuity mistake: When they are inspecting the outside of the house, one of the dogs brings to Marta the piece of trellis she broke. She holds it in close-up with the loop facing upwards, but as it cuts to Blanc shouting "Sweet beans!" the circle is pointing down. (00:59:00)
Continuity mistake: Blanc is questioning the security person of the estate. In the close-up you can see him pin a picture to the board using one of the magnets. To the right there's a banana magnet. The tip of the banana on the bottom touches exactly the border of the picture almost in the corner, but in the wider angle we see the photo continues half an inch lower. (00:55:00)
Continuity mistake: Marta tries the back door of the apartment and stumbles upon Walt. When they talk, she fiddles nervously with her mail and brings up an unmarked envelope, which should be on top of everything since she just dug for it. When she retreats into the kitchen, she puts the mail pile on the table; in the first shot there's a bunch of business cards on top of everything; after a view of her face and upper body when she is not messing further with the letters, there's a close-up of her going through the mail, and the unmarked envelope is exactly on top, with the cards gone. (01:26:10 - 01:28:15)
Continuity mistake: After the reading of the will, the family storms the lawyer. Linda is reading the will holding it in both hands, which becomes one hand at the cut. (01:10:25)
Continuity mistake: Blanc says he has no idea how Fran got hold of the toxicology report; in that shot, wide angle, Marta's hair cover her right side of the collar of her coat, like in most of the scene. But in the close-up that follows, when she blurts out of the reason, her hair is on the inside of it. (01:54:10)
Continuity mistake: During the explanation of the events, Ransom angrily replies to Blanc "You have her confession" as he objects that there's no proof about the vial switch. Daniel Craig says "All right, yeah" arms down, but in the next shot he is shown at the edge of the frame during Marta's closeup, and his arm is bent. During that close-up Ana de Armas ' hair is also differently spread over the shoulders compared to the following view. (01:52:10)
Continuity mistake: Ransom is brought back in the room for Blanc's denouement by Officer Wagner. First shot he has his hand under Ransom's armpit. Second, Chris Evans' arm is close to the body, no officer hand in sight. Third like the first, hand under armpit. Fourth, the officer is a few steps away and with his arm lowered. (01:46:20)
Continuity mistake: Ransom's presence has been incendiary, and everyone is arguing. Walt and Richard get into a slapfest pawing at each other, and Ransom in a close-up says "We gotta do this more often", eating the biscuit. At the cut with Linda shouting "Hey!" and shutting everybody up, Ransom is in the background just contemplating the cookie still in his hand. Similarly, later when Jacob says what he heard and everyone looks at him, he is chewing in the background, but puts his cookie in his mouth in the close-up. (01:02:35)
Answer: To add slightly to the other answer, evidently some of the blood in the scene had to be digitally removed for the film to secure a PG-13 rating, which explains why we don't see any actual spray/gush. But we are to assume that a drop managed to splash onto her shoe when he slit his throat.
TedStixon