Custom Model does not allow me to use images generated by previous Custom Model?

I successfully made my first style custom model, "Model 1". I generated some images from the "Model 1" which I thought were good examples of the style. So I wanted to add those to the style. 
I made a duplicate of the "Model 1"   as "Model 2" and uploaded several of the newly created images from "Model 1" to add to the new set of images. The tool rejected most but not all of th images I tried to add that were generated by "Model 1". It did not give an explanation of why these images were rejected.  

In the attached image you can see the rejected images along with some of the existing images of the original style "Model 1".

Is there an explanation for what is rejected?  Any rules we need to know about?? 

reject-custom-model-made-images-1.png