This is a bug I don’t understand, usualy when I split parts of the objects it keeps all the materials and the shaders they have.
I was trying to change user prefs \ settings to link materials to: Object \ Object Data etc, does not help.
I’ve never tried this before but have you ever tried separating by materials?
It looks to be caused by materials on the robot being linked to object instead of the mesh datablock. I just tested here and indeed in that case, if you separate something that’s using a material slot other than first one, it gets no material.
Whether it’s a bug, I don’t know. Might be a good idea to report it anyway though.
All the options act the same way
Thank you, I found it as a bug.