The provided carpaint_color_peel_2_layer.shader will generates a fragment shader with two outputs:

out vec4 fragOuput;
...
out vec4 fragColor;

This violates section 14.2.3 of the ES 3.2 spec (https://www.khronos.org/registry/OpenGL/specs/es/3.2/es_spec_3.2.pdf), which states: "If there is only a single output variable, it does not need to
be explicitly bound to a fragment color within the shader text, in which case it is implicitly bound to fragment color zero. If there is more than one output variable, all output variables must be explicitly bound to fragment colors within the shader text. Missing or conflicting binding assignments will cause CompileShader to fail."

and produces the following error:

error: fragment shader's output location has to be explicitly specified

It is also possible that other materials in the material library will have the same issue.