I was creating a SkyWars map, and I wanted to clone an island with structure blocks. But I wasn't expecting that traps doors kept their original orientation. So I save each island individually. That is not a big bug, but it is a little annoying. 

_Additional information from jirauser521040
When using structure blocks to copy and paste builds/structures, trapdoors are not copied over accurately when the structure is rotated or mirrored. It is less noticeable when the trapdoors are on the horizontal, but very noticeable when vertical as their position completely changes from it’s origin.

To reproduce:

1. Create a flat world in creative. 
2. Use the /give @s command to get a structure block
3. Get snow blocks from your inventory and create a platform that is 7x7 by 1 high. 
4. Get a locator map and open it.
5. Align the arrow representing the player to point South which is the bottom of the map. 
6. Build a wall out of snow blocks on the South side of the platform that is 5 blocks high, 7 blocks wide and 1 block deep. 
7. Place 5 spruce trapdoors on the wall and 5 spruce trapdoors on the floor in any direction as long as it is the same for all of them. 
8. Flip each of the trapdoors to be vertical.
9. Place the structure block on the bottom right corner of the platform when facing the wall (North-West corner).
10. Open the command block and name the structure "Test1".
11. Change the three numbers on the left of the screen to 7. 
12. Press the "Save" button at the bottom of the screen..
13. Change the top drop down menu to "load".
14. Change the first number (Next to the red X) to 9 to offset the structure. 
15. Either rotate or mirror the structure using the slider or button labeled in the structure block menu options. 
16. Press the "Load" button at the bottom of the screen..
17. Exit the structure block.
18. Observe that the newly placed structure’s trapdoors are not in the correct position and were rotated incorrectly during the process. 

Observed results:
Trapdoors are not rotated properly when the structure block is used and that the player has selected that the structure be rotated or mirrored.

Expected results:
When using a structure block, the entire structure is properly copied and pasted and the trapdoors that are pasted are rotated or mirrored in the same manner that the player choose to rotate or mirror  the entire build.