Thanks! I updated my site from the master and it now works.
How to hide group members (or show title of hidden group)
is there a way to setup a group so that the member list is not shown on the group page?
I know of the "hidden" property, which hides the group as a whole in the group list and makes the group page not reachable. This would be OK if only it didn't hide group titles as well - so the question may also be "is there a way to allow users to display the title of an hidden group they're members of"?