while it was the correct picture/image, it ended up being off-center and zoomed without being able to correct it.
The explanation is simple: backup apps are unreliable. They only have different limitations. Swift is no exception, as I'm finding many.
This is how you may investigate:
[Root]/data/system/users/0/wallpaper_info.xml
This file carries the wallpaper settings.
I would compare this file before and after customizing the wallpaper to memorize the differences.
Then I would back it up and immediately restore it using Swift
If there is a difference between before and after the backup, you found the cause.
Since I grew tired of relying on these backup apps, I make manual copies of these files you will see around these folders, the folders beying /data/system/, and /data/system/users/0