Occasionally, breaking a Shulker box breaks the box but does not drop the box (or the drop is invisible?)

The world in question is a Survival Microsoft Realm. I restored a snapshot which shows the box floating where it should have dropped. I don't know if this means it was invisible and not able to picked up or something else.

This has happened on 3 boxes for me so far, in roughly 300 hrs of play. This is the first time on 1.21.2. Other occurrences were under 1.20.xx.
I am filing this under windows, though at least one of them occurred on the Nintendo Switch (all the same realm).

No mods are used.

All were dyed (2 yellow, 1 orange), the most recent was named. Contents were all various redstone components, mostly all stackable. Boxes were not totally full.

The most recent box was broken with a Diamond pickaxe with Fortune 3, Unbreaking 3, Efficiency 5, Mending. Box was sitting on a grass plain in sunny daylight weather.

This doesn't appear to be the same as any of the other shulker bugs posted recently, as it occurred on the most current version as of this posting, and was broken with an axe, not a hand. It is also not clear what makes it happen, as it works most of the time.