List of Emails - 500 Error

We are using Drupal 7.80 with SQL Server 2016.

Problem/Motivation

When I navigate to "Form Submissions" inside a specific entity form, it displays previous submissions. There are three buttons to sub-navigate. The "Page" and "Table" links work correctly. The "List of Emails" link is not working, however. When I click it, there is a delay then I get a 500 Page error.

This page isn't working ... (this page) is currently unable to handle the request... HTTP Error 500

Steps to reproduce

1. Go to Structure/Entityform Types
2. Choose an existing form and click the "Submissions" link
3. From the submenu, click "List of Emails"

I'm wondering if anyone has any ideas for testing or a resolution. It is timing out, but I don't know why. This doesn't appear to be critical at all. I'm not even sure what "List of Emails" shows. It might point to a larger problem with entityforms, however.

Thanks in advance for any ideas.