I run a c5 instance with a particular setup. I have one direct login account, which is "webmaster". All of the user accounts sign in via the Google sign-in module. (I set it up this way because we have a G Suite domain, so why bother having people remember yet another set of credentials?)

I added my own user account to the admin group, and then log out. The idea is that all changes can now be tracked according to individual users, and we never have to wonder "who was logged in as webmaster when this or that change happened?"

So far so good. Here's the problem. When I click on the Members list to view all of the user accounts, only other admins show up. That means the default Webmaster account, and one other admin that I added. None of the other users show up by default unless I log out and log in again in the native c5 login module using that webmaster account.

At first I thought this was down to some bad configuration, but now I'm almost sure it's a bug. Because…

STEPS TO REPRODUCE
1. Log in to my admin account using Google sign in module.
2. Navigate to the members list. At this point only other admin accounts are shown.
3. Click "Customize results".
4. Click "Save". (It's not necessary to make changes.

RESULTS
If I follow these steps, now all user accounts are populated in the member list, as they should have been when I first loaded it.

With a bit more experimentation I figured out that a user must be added to a group in order to initially appear in the members list. Users not in any group disappear until I do the "Customize results" trick above.