Visible crew/equipment: When Mrs. Peacock turns on the cellar lights, a piece of lighting equipment is visible to the left of the screen. (00:47:45)
Continuity mistake: When they enter the kitchen to check on the cook, a pot on the stove disappears and reappears.
Continuity mistake: When everyone is searching upstairs and Miss Scarlet and Colonel Mustard start screaming, they all come running down. Yvette and Miss Scarlet have on flat black shoes, but right after the running shot is over, both are back in heels.
Continuity mistake: When they reach the study with the dead cook's body, they stop before entering and drop her half-way into the room. They proceed to look for Mr. Boddy in the room and file into the Study one at a time. In the same camera angle you see everyone entering the study including Miss Scarlet, then Yvette, then Mrs. White. Then the camera angle changes and in comes Scarlet, White and then Yvette.
Continuity mistake: After Mrs. Peacock says "Mmm, this is one of my favorite recipes" each time the camera angle changes at the table her fur boa changes from up to down for a few shots.
Continuity mistake: The Singing Telegram's body position changes when everyone finds her. (01:04:45)
Continuity mistake: When Professor Plum is sitting on the couch between the corpses of the Mr. Boddy and the Cook, Mr. Boddy is lying in Professor Plum's arm, in the next shot when Colonel Mustard, goes to close his eyes, he is now lying next to the arm of the sofa.
Continuity mistake: Colonel Mustard pours everyone a drink, he puts the whisky on the table and in the next shot the glass he poured whisky in is in his hand without enough time to pick it up. In addition, he puts the decanter down closer to him in the close-up, than it is in the medium long shot. (00:41:15)
Suggested correction: She was shot, not switched off. She likely didn't die instantly. It's perfectly reasonable that she would move her arm as she was dying.
She died instantly, that is why she collapsed instantly. I am still wondering why they didn't make it look like a real shot, and have blood around the area she was shot at? They made it look as though she was wearing a bulletproof vest and was shot. You can see silver, no blood.