Note: the 'warning' signs do not indicate that something is wrong in the shader.

They only indicate that some elements of the selected material shader cannot be viewed in the Simple Material Room display, but only in the Advanced display.

All but the very simplest shaders will have something that can't be shown in the Simple display. A little familiarity with the Advanced display and you'll use it for everything, since it actually gives a more logical view of what's going on.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)