Gallery thumbnails only appear using default gallery media field

I created a default node gallery content type which you see here in image:

The content type is "Gallery Item". The image field is "Gallery Media", field type "File". This is the default created during Node Gallery install.

However, I wanted to use Lightbox and ImageZoom, which require an "Image" field type. So, I added an Image field "Gallery Media 2" which you also see in the attached image. I then changed the default relationship for Gallery iterm to use "Gallery media 2" as the image field:

This pretty much works as expected and I can now zoom gallery images.

However, if I delete images from the original "Gallery media" field, the image thumbnails no longer appear on the Gallery display. Now, I did set the mediafont settings to use node_gallery_thumbnails as you see here:

But, the gallery item thumbnail images still do not appear in the Gallery node display -- only the image titles.

Any suggestions?

Thanks!