When creating a saving a Structure using a Structure Block Block Displays don’t get saved properly.
Environment
Open a World in 1.21.8
Summon Block Display (With data, i.e. what block it is)
Place Structure Block and make sure it encompasses the Block Display and save
Place another Structure Block and load Structure you saved
Linked issues
Attachments
Comments 3
This is just MC-103452. The workaround is to run /execute as @e[type=minecraft:block_display] run ride @s dismount before saving the structure.
In my own test, I could not reproduce this issue. Please provide a copy of your world.