Unknownreported this bug
Interestingly, these two files were loaded successfully in ItemsAdder 4.0.3, but after upgrading to version 4.0.5, they now fail to load.
I'm not entirely sure what is causing this issue. Should Mythichud update these shader files, or should ItemsAdder provide compatibility for them?
Therefore, I've decided to report this issue to both parties to determine where the problem lies and how it can be resolved.