So I’ve forked this project to test it. First thing is console straight away spawning with warning when material is changed:
[.Offscreen-For-WebGL-0x70da6e8de00]GL ERROR :GL_INVALID_OPERATION : glDrawElements: attempt to access out of range vertices in attribute 2
You could have mentioned this before, as this is pointing to an issue.
I will investigate further into the problem. It seems like model format you are loading is wrong. Error suggests that number of attribute elements is wrong, either you defined Vertex Buffer format wrong, or provided wrong data to the buffer.
Issue could be in Mesh.js file.