Preheat the oven to 350°F and prepare a baking sheet by lining it with parchment paper. Spread the oyster crackers evenly across the lined sheet. In a medium saucepan set over medium heat, melt the butter, then add the brown sugar, vanilla extract, and cinnamon. Stir continuously until the mixture is fully blended and begins to bubble. Let it boil gently for 2 to 3 minutes, stirring constantly, until it thickens slightly and takes on a lighter hue. Remove the saucepan from the heat and immediately pour the hot caramel mixture over the crackers. Gently fold the mixture with a spatula to ensure every cracker is well coated. Sprinkle the salt over the top. Place the tray in the oven and bake for 7 to 9 minutes, carefully monitoring to avoid burning the caramel. Once baked, let the crackers cool completely before breaking them into clusters. Store in an airtight container to maintain crispness.