The bug
Cannot get the data from certain blocks.
How to reproduce
Aim a block and type this command (with block coordinates instead of tildes):
/data get block ~ ~ ~
Example with new blocks of 1.14
Here is an example in video with the new blocks of 1.14:
[media]
Duplicate of MC-151043.
You can only use
/data get block
on blocks that are block entities. Crafting tables, stonecutters, etc all have a GUI, but don't have any data stored in them that could be modified.