When sprint-jumping through banners placed on the ground, the sound for footsteps on wood plays while the player is in the air. Very simple to bug to recreate. Just place a bunch of banners in a straight line on grass or something that does not play block.wood.step and walk through them while jumping. The footstep sound will change to wood and continue playing as the player jumps.

Bug first experienced in 1.16.5 on Optifine, but I tested it again on 1.17 vanilla, and found the same results. May have been around a while.