Missing Camera and Lens Metadata after iPhoto Import

I've noticed that the Photos for Mac app seems to have "lost" all of the Camera and Lens Metadata associated with each of my photos. Has this happened to anyone else?

No matter which photo I choose, the Info inspector window shows "No Camera Information" and "No Lens Information". I've confirmed that the Camera and Lens metadata is still present in the original iPhoto Library.

If I create a new iPhoto Library with just a dozen or so pictures and then choose that Library when launching Photos for Mac, by pressing the Option key while clicking the Icon, the photos are imported with the Metadata intact. Clearly something went wrong with the import of my much larger main iPhoto library. (The main library has over 100,000 photos in it.)

I'm wondering if there is some way to force Photos for Mac to re-index the Metadata. Any thoughts?

Thanks,

Michael