The bounding box of the structure blocks in save mode reflects the rotation selected in the load mode, despite the rotation having no effect on the save mode.

To replicate:

1. Enter a world with cheats
2. Place down a structure block in save mode, and select the area you want to save
3. Use a another structure block in load mode somewhere else to load it
4. Return to the save block. Set it to load mode, and select a rotation. Ensure that the bounding box is no longer around your original structure
5. Return the original structure block to save mode, and notice that the bounding box does not return to its correct location
6. Save the structure and load it again. Notice how the structure saved correctly, even though the bounding box is misplaced

Demonstration video