Erica,
I don’t see any errors being output when trying to edit the image meta data.
I tried removing other plugins on the same page (I’m using a different video gallery plugin on that page) and that didn’t fix it. I haven’t tried disabling all other plugins or reverting to the Twenty-Sixteen theme though I don’t believe that would be the issue since there are some that are being displayed and others that are not.
In reply to your last paragraph, if that’s the case then I should be able to edit the caption that’s being displayed in the lightbox but I don’t see an area in the Envira gallery plugin to be able to edit the caption. I only see inputs for a Title, Alt Text and URL. Is there another place where I am able to edit this information per image?