Shulker boxes occasionally, when placed, cannot be opened and when re-mined, will not drop, causing the player to lose all the items in the box. (I saw this bug reported here at one point but can no longer find the report, so I thought I'd create a new report. If the other report still stands, I'm sorry for duplicating.)
Linked issues
Comments

Duplicate of MC-131288.
Please use the search function next time. This makes the reporting process easier for you and the moderation team.