Powder snow bucket in a dispenser at y = 319 facing upwards or at y = -64 facing downwards is replaced with empty bucket, despite no powder snow being placed

The bug

Powering a dispenser containing a powder snow bucket pointing upwards at y = 319 or downwards at y = -64 replaces the full bucket in the dispenser with an empty one, despite no powder snow really being placed.

Closely relates to MC-117806.