Problems with Bake. The maps are not baked.

I bake the building 1 , a few days ago and the bake was correct. 
Today I saved a new .obj with Building 1 and more buildings and I got the problem in "Problem_01 and Problem_01_2" pictures. 
The "building 1" is correct. The rest are shown as if the UVs were overlapping, which is not the case. As it can be seen  in the image "UVs_no_result_bake".

When I open the .obj of "building 1" separately, ithe bake is fine. 
I did save any of the other buildings separately in an .obj and open them 1 by 1 for  baking. I get the "problem_02" in the image. It doesn't generate the mesh maps. Not even as it was doing on the .obj where is the "building 1" 

I have checked all the buildings and they have no triangles, no Nside or any layer errors. 

Which can be the problem then? 

Thank you