Whisk together the flour, sugar, baking powder, baking soda, salt and cinnamon in a large bowl. Add the buttermilk and eggs. Whisk together, gradually incorporating the flour mixture, just until combined. Add the banana slices and gently combine; the batter may be slightly lumpy. Let stand 10 minutes.
Place a griddle pan over medium heat. Add the canola oil and butter. Using a ladle, pour 1/2 cup batter for each pancake, roughly 2 inches apart. When small bubbles appear across the surface of the pancakes and the edges lift from the griddle, flip and continue cooking until the pancakes are golden brown on the second side, about 4 minutes per side. Continue with the remaining batter.
In a small dish using a rubber spatula, mix the peanut butter and maple syrup until combined. For each sandwich, spread some peanut butter mixture over a pancake, then top with another pancake.