recently i noticed working on one of my files that the subobject materials have been overriden.
i can copy both into a new file and there it exhibits both versions, but when i copy the correct object from an older backup into the working file the texture gets overridden, i can not rebuilt all objects, is there anything else i could try besides waiting for a fix (if that is a bug at all). to be frank i have no idea how that happened since i did not touch the texture of these objects in ages, so i assume something happened with Rhino instead.
I see the sub-objects on the black sided box as still having a sub-object material, the one named MPsignal. It just doesn’t have a texture map in the color channel. I added a checker texture to it and the sub-object material assignment shows it. My guess is you removed the texture used in this material originally and when you next opened the model may have clicked Continue to the message saying that a texture used was not found or removed the unlocated texture from the message at that time with the Remove option.