Powder snow layers in cauldrons are inconsistently removed in creative mode

The bug

Powder snow layers are inconsistently removed while swapping the contents of a cauldron from lava to powder snow, while a player in creative mode is standing inside the cauldron.

How to reproduce

1. Enter creative mode, if you are not already (/gamemode creative) 
2. Place a cauldron, and fill it with lava
3. Place a trapdoor on top of the cauldron, and open it. This will ensure that you don't mis-click and place lava/powder snow outside the cauldron.
4. Stand inside the cauldron
5. Swap the lava out for powder snow, and take note the results (was a layer of the snow removed?)
6. Swap for lava and back to powder snow as many times as you would like,
    Notice how the cauldron occasionally loses a layer of powder snow, and occasionally stays full of powder snow

Video

Video of this issue occurring (0:40): https://youtu.be/oEvP69IMcUc