Whisk the flour, sugar, baking powder, baking soda and salt together in a medium bowl. In a second medium bowl, whisk together the buttermilk, sour cream, eggs and melted butter. Make a well in the center of the dry ingredients and pour in the wet ingredients; gently stir until just combined (batter should remain lumpy with a few streaks of flour). Do not overmix. Allow the batter to sit for 10 minutes before cooking.
Heat 1 teaspoon of the vegetable oil in a nonstick skillet over medium heat until shimmering. Using a paper towel, carefully wipe out oil, leaving a thin film of oil on the bottom of the pan. Using ¼ cup measure, portion batter into pan in 4 places. Cook until edges are set, first side is golden brown, and bubbles on surface are just beginning to break, 2 to 3 minutes. Using a thin, wide spatula, flip pancakes and continue to cook until second side is golden brown, 1 to 2 minutes longer. Serve pancakes immediately. Repeat with remaining batter, using remaining oil as needed.