The bug

Using data merge block on a structure block to edit its mirror or rotation does not change the way the structure is then loaded unless the world is reloaded.

How to reproduce

1. Save a structure
2. Place a load structure block and write the name of the structure you have saved
3. Click load
4. Execute

   /data merge block x y z {rotation:"COUNTERCLOCKWISE_90"}
   

   with x, y and z being the coordinates of the structure block

5. The bounding box does not update
6. Click load again, the structure loads like it would have without changing rotation