Shulkerboxes pushes Armorstands up and pull it down again, when you open them quickly. If you open then longer the armor stand glitches in the shulkerbox falling down. When a player is standing over the shulker box there must be a block above to reproduce the bug.
16w40a: Only glitches if the shulker block pushes a player, armorstand, etc... against a block.
Linked issues
is duplicated by 7
MC-107952
mobs glitch in shulker box wen open
Resolved
MC-108108
Entities Glitch When On Top Of Opened Shulker Box
Resolved
MC-201585
If standing on top of shulker box with roof above you fall right through
Resolved
MC-235590
A bug with the schalker box and the schalker mob.
Resolved
MC-241153
Glitch shulker box to go under the ground
Resolved
2 more links
relates to 4
MC-107954
Camera shakes when open shulker box you standing on
Resolved
MC-108063
Falling death/hurt, when player riding pig or horse / boat to the top shulker box and open it
Resolved
MC-134550
Entities inside of cobwebs on top of a shulker box clip through it when opening the box
Open
MC-83176
When standing on shulker you have a chance to fall into it and get stuck
Resolved
Erik Broes
It is not completly fixed. If a player or Armorstand, i guess any high enough entity is pushed from the Shulker Box agains a solid Block, it still glitches