OpenMW-CS does not support shader rendering
All the changes to the shader rendering across the last few years made OpenMW-CS incapable of rendering things with shaders. While shaders aren't actually necessary to render most things, this becomes a problem when things force shader rendering, e.g. if the mesh uses a bump map, like the one here: a_indoril_m_helmet.nif
Use such a model for an object and try to preview that object. You'll run into undefined everything errors and will have little success at seeing the object.