Same here. I did some mesh fixing using MeshMixer on a model exported from RC (that was unwrapped and textured in RC), after cutting away some triangles and introducing new ones (which were unwrapped automatically by MeshMixer), when importing the model back into RC to re-texture, RC through this error: “The model contains non-textured triangles. Please update the model UV coordinates and try to import the model again”.
Importing models with or without UV’s into RC was NOT a problem before version 1.2 and I think it could break a lot of people’s workflows!