What are these dark areas (shadows?) on an NPC with Quest 3 passthrough - screenshots included

Hey 🙂

I'm a newcomer to Unity/Meta development, I've created a small app whereby I can chat to an AI powered NPC in passthrough. It works ok, however on my NPC there are dark/black areas, not sure if they are shadows, I'd like to know how to remove them please?

I'm using 3D Core, the Unity version is in the screenshots. I've tried experimenting with Directional Light but have had no luck. Any help would be really appreciated.