Going down on the edge of powder snow stops sneaking for a moment

Summary:
Going down on the edge of powder snow causes the player to stop sneaking for a moment. No slowdown on the edge of powder snow is tracked in MC-227191.

Steps to reproduce:

1. Build a tower of powder snow.

2. Move partially inside it, but make sure that your center is not inside it.

3. Move downwards by pressing the sneak key.

Observed results:
While moving on the edge down in powder snow, the player stops sneaking for a moment.

Expected results:
The player will not stop sneaking unless they stop pressing sneak key.

Video:

Original Description:
If you stand partly outside a powder snow pillar with leather boots on and crouch it should be smooth falling like scaffolding but is jittery. see clip. 

https://clips.twitch.tv/KathishWiseOtterBCWarrior-ySkiafVQIt1ipPqO