With the latest non-beta version, I found out that I can only change the lock screen background image once.
Steps to reproduce.
1. Start Decor8, and go to Lock Screen section.
2. I then use the 'Select File' function, select an image for the new lock screen background.
3. I then click the 'Apply Selected Background to my lock screen' button to make the selected image my lock screen button.
4. The lock screen background image will be successfully changed, but the 'Apply Selected Background to my lock screen' button will stay greyed out.
5. I then use the 'Select File' function again, to select a new image for the lock screen, but I cannot apply the new image as my new lock screen background image because the 'Apply Selected Background to my lock screen' button is greyed out.
I have to restart the Decor8 program just to change the lock screen background image again.