The bug

On controllers you can toggle sneaking. If you hold down the sneak button on top of a scaffolding, you will climb down and if you briefly press the button, you will sneak until you press it again without climbing down. That is all correct. But I belive the problem was introduced in 1.13: Now when you do that you will also climb down by one block.

How to reproduce:

1. You need a controller, should also work on windows 10 when using a controller
2. Make a scaffolding tower
3. Stand on top
4. Press your sneak button (by default RS), but don’t hold it down, just press it briefly

Observed result: You will climb down by one block and then stand still and continue sneaking.
Expected result: You will just start sneaking and stand still without also climbing down. I am very sure, that this used to be the case in 1.12.