Bruh, i think this is a bug. For some reason, anything in the category of usermesh just stops rendering for a mystical reason.
For example i took 2 prototype objects existing in wildlife already, put them togeter and created a combined mesh out of them which automatically converts it into a usermesh. As soon as i combined them they disappeared. Funny enough Wild Life does prompt you to save the new combinde mesh as an .obj externally, so i figured to open it up in blender, and yeah, the mesh exists and blender has no issue opening combined user meshes created in wl.