DDUI elements missing or broken

DDUI elements missing or broken.

How to reproduce:
1. Download my example DDUI script
2. Import the pack into minecraft
3. Activate the pack and make sure experimental features are on
4. Load into the world
5. Right click on a book to open the DDUI screen
6. Observe the DDUI background and switch icons missing
7. Close the DDUI screen, then go to settings from the game menu
8. Observe Ore UI switches now missing their icons