Steps to reproduce:

1. Create a new world and place a decorated pot/shulker box
2. Put something in it
3. Pick the block without holding Ctrl

Observed result:
In survival mode, nothing will be selected.
In creative mode, you will get a new decorated pot/shulker box with the same items in it.

Expected result:
The original decorated pot/shulker box item will be selected, which means only the "sherds" tag in the decorated pot block entity data is retained.

Note:
The issue cannot be reproduced for other container blocks.