You can repair the textures by yourself. Go down to the outerra directory -> C:\Users\{your_name}\Outerra\packages\{your_name}\{your_object}. You will find a file with a .mtl extension. Open it and add the name of the diffuse texture after tex_albedo. It must be look like this: "tex_albedo" : "wall1_tex.dds",
. And you have to copy the texture file to this directory.
After tweaking the material file you have to restart outerra.