While not currently possible to access when playing this mod with vanilla mobs, any mob which has a shader vision prevents the player possessing it from seeing things like the escape menu, inventory, or chat bar.

Almost an entire year later
I (partially) fixed it! It is available at the Legacy Dissolution repository or at the latest 1.12 file uploaded on CurseForge. Thanks for reporting this bug even if there was no support for this mod for nearly a year!