Could you somehow not have them in a group and just separate meshes, not related in between them in anyway and THEN attach them all together?
Did you also convert all geometry to mesh before attaching?
It seems that the exporter still thinks it has multiple meshes, at least, it's responding more accurately now.
The exporter should error you if there's more than one mesh.
My guess is that you only have one mesh and the rest are polys or something else.
Convert all of your wall to mesh select only one part of it and in the edit geometry rollout or whatever it is called click the "attach" button and attach the other meshes.
Could you somehow not have them in a group and just separate meshes, not related in between them in anyway and THEN attach them all together?
Did you also convert all geometry to mesh before attaching?
It seems that the exporter still thinks it has multiple meshes, at least, it's responding more accurately now.
The exporter should error you if there's more than one mesh.
My guess is that you only have one mesh and the rest are polys or something else.
Convert all of your wall to mesh select only one part of it and in the edit geometry rollout or whatever it is called click the "attach" button and attach the other meshes.