At the end of Knives Out, Ransom tries to stab Marta with a fake (prop) knife, but it collapses into the handle, saving her life, but it makes no sense why there would be a fake knife on display in the first place.
Many of the knives around the house are real, as demonstrated by Harlan earlier in the film, where he foreshadows the ending by explaining that Ransom is “Confident, stupid and protected, playing life like a game without consequence until you can’t tell the difference between a stage prop and a real knife,” then demonstrating that the knife is, in fact, real by stabbing it into the table. This explains why Ransom chose the wrong weapon but it doesn't explain why there is a fake weapon up there in the first place.
Harlan is clearly an avid collector of bladed weapons, just look at the display rack where he has all manner of axes, swords and knives. The knife Ransom chooses to stab Marta with is one of the only knives that could be a prop as its blade is smaller than the grip. Given the choice between larger knives, axes and other deadly weaponry, Ransom picked the worst option out of over a hundred. All of this just seems implausible to me.
Why would there be a fake knife displayed amongst the deadly weapons and why would Ransom pick one of the only fake weapons out of hundreds?