Unity ECS materials are grey on Build and Run

Hi,

On an ECS project on Unity 6, after hitting Build and Run, some materials are grey.
It doesn’t matter whether I choose a production or dev build.
The funny thing is when I launch the app I get different results everytime.
Sometimes the characters are grey, sometimes the ground is.

Does anyone have a fix for this?

Reverting to Unity 6000.0.18f1 fixed the issue.