You cannot climb scaffolding, when you press the jump button to climb you will sink back to the floor instead of climbing to the first scaffolding block to stand on it. This bug can happen randomly and might go away the if game is reset.
MCPE-240286
Cannot Climb Scaffolding
Resolved
Awaiting Response
0
Does this only happen when you are wearing elytra? Could you record a video from the third person view?