Why is this bake wrong on one side of the X axis? I'm trying to bake down some textures for use in a different engine.  I've got a problem I haven't seen before.



I'm showing a rendered preview so you can see it's not the mat nodes, and a textured preview so you can see that the bake is completely wrong on one side, and one side only, of the face.

Things I've already checked:

It is all one object.  The object has no modifiers.  There is no UV overlap.  Other than the boundaries for the eyes, mouth, and neck, and the fact that the eyelashes and eyebrows are separate meshes, the mesh is manifold (ie, normals are all continuous and facing the correct direction.)  The model has smooth shading, with autosmooth disabled.  I've cleared custom normals.  Rotation/scale/location have all been applied.

The only clue I have is that it warns me that there is no active image for one (unimportant, not really shown here) material, even though that material definitely does have an image texture, referring to the image, as the active selection.

What else can I check here?  http://www.mediafire.com/file/ucj6r1fqypr7dou/bakesFace2.blend/file is the file, although sorry, it is pretty large.

Edit: I've resolved this issue-- I thought, "hey, I should probably stitch those UV halves together" and lo and behold, afterwards, it baked right.  But still interested in why this occurred.
I guess you didn't select the good UV Map in the Data panel, i.e. the one that has been used in the Node Editor for your face material, as you can see on this screenshot: